jw^^^sr^^^^2nw^.% ' 'Str^^

|J> W '.•?■%.. ^ fa,- W!J5»' ■»3,^- fcS':;^; «»?'> .%?^: ft?^. .^^»ly ^li'.-, -vi^, -,,_,

tfiBte ' aqp'itftnwpriw*!^ 7)r»r,--vtw.gsMWfi'-,'yfyr:tfv-'i-*/nf:-cs>-'n,'.-

% lj''^'\

H^ .;»'*?

■ -) ■_ ,

I.'>".-,S« -fW j«-»' ►'Jif J¥J^ !•<

iDiTED byJ.sk mc

-■^■^

t-V,-J7!-.'-^'Jfi>-rt/.

I i^^\V ^;if^!* ^?-^ '^* r¥^»' ^'if^*^^ '

,■ •AMMMTMUwa^WISAia.-:

^■;:t

i ^LIBRARYOF>^ ii

I ^-^ H/«^. I

I

S

"a-

-iPAI

€1>

■Vp „: J;"J

'■y^f

l>'

NATURAL HISTORY OF INVERTEBRATES.

SAMUEL F. CLARKE, Ph.D. D. S. KELLICOTT, Ph.D.

J. WALTER FEWKES, Ph.D. J. S. KINGSLEY.

EOMYN HITCHCOCK. W. N. LOCKINGTON.

ALPHEUS HYATT. CHARLES S. MINOT, D.Sc.

ALPHEUS S. PACKARD, Ph.D.

Cuciimaria hyndemanni, sea cuciinibei-.

THE STANDARD

NATURAL HISTORY.

EDITED BY

JOHN STERLING KINGSLEY.

Vol. I.
LOWER INVERTEBRATES.

muistvatett

BY FIVE HUNDRED AND ONE WOOD-CUTS AND TWENTY-TWO
FULL-PAGE PLATES.

IBostou:

S. E. CASSINO AND COMPANY.

1885.

Copyright by

S. E. Cassino and CoMPAirr,

1884.

C. J. PETERS AND SON,

steeeotypers and electhottpers,
145 High Sikekt.

\

C O N T E i^ T S.

PAGE

ISTRODUCTION 1

Bkanch I. — Protozoa 1

Class I. — Moneka 2

Class II. — Rhizopoda 4

Class III. — Gregarinida 23

Class IV. — Infusoria 26

Branch II. — Porifer.\ta 49

Class I. — Calcispongi^ 61

Class II. — Carneospongi.e 63

Branch III. — Ccelexterata . . . 72

Class I. — Hydrozoa 73

Order I. — Hvdroidea • 73

Order II. — Discophora 89

Class II. — Siphonophora 97

Order I. — Puysophoe.s: . . . .■ 98

Order II. — Pneumatophor-« 104

Order III. — Diphy.e 105

Order IV. — Discoideje 107

Class III. — Ctenophora 108'

Class IV. — Actinozoa 112

Order I. — Zoantharia 116

Order II. — Halcyonoid.\ 121

Branch IV. — Echinodekmata 135

Class I. — Crinoidea 139

Order I. — Blastoidea 139

Order II. — Cystide.a. . 139

Order III. — Bracuiata 140

Class II. — Stellekida 147

Order I. — Opuiuroidea . . . • 147

Order II. — Asteroidea 152

Class III. — Echinoidea 161

Order I. — Desmosticha 164

Order II. — Clypeastrid.e 170

Order III. — Petalosticha 172

Class IV. — Holothuroidea 176

Order I. — Ei.asipoda 179

Order II. — Apoda 179

Order III. — Pedata . , ISO

Order IV. — Diplostomidea 183

CONTENTS.

Branch V. — Vekmes 185

Class I. — Platuelminthea 187

SUB-Cl,ASS I. — Turbellaeia 188

Sub-Class II. — Trematoda 191

Sub-Class III. — Cestoda 198

Class II. — Rotifera 202

Class III. — Gastrotricha 206

Class IV. — Nematoda 207

Class V. — Acanthocephali 21.3

Class VI. — Cu.etognathi 213

Class VII. — Nemertea 215

Class VIII. — Gephybea 217

Class IX. — Annelida 218

Sub-Class I. — Archiannelida 219

Sub-Class II. — Ch^topoda 219

Sub-Class III. — Enteropneusti 231

Sub-Class IV. — Discophoei 232

Branch VI. — Molluscoidea 2.36

Class I. — Polyzoa 236

Sub-Class I. — Entoprocta 239

Sub-Class II. — Ectoprocta 240

Sub-Class III. — Podostomata 244

Class II. — Bracuiopoda 244

Branch VII. — Mollusca 248

Class I. — Acephala 252

Class II. — Cephalophora 287

Sub-Class I. — Scaphopoda 291

Sub-Class II. — Gasteropoda 292

SUPER-OltDER I. — Isopleuba 292

Order I. — Ch^toderm^ 292

Order II. — Xeomenoidea 292

Order III. — Polyplacophora 293

Super-Order II. — Anisopleura 294

Order I. — Opistiiobrancuiata 295

Order II. — Pulmonata 303

Order III. — Zygobranchia 319

Order IV. — Scutibranchia 322

0i!DER V. — Ctenobranchia 324

Order VI. — Heteropoda 353

Sub-Class III. — Pteropoda 356

Order I. — Thecosomata 357

Order II. — Gymnosomata 359

Class III. — Cephalopoda 360

Sub-Class I. — Tetrabranchiata . . . 367

Sub-Class II. —Dir.RANCHiATA 369

Order I. — Octopoda 369

Order II. — Decaceea 372

LIST OF PLATES.

PAGE

Sea Cucumber Frontispiece

polystomella 16

Sponges 56

Dalmatian Sponge Fishery 64

gorgonia verrucosa 72

Tubularian Hydkoid 80

Hydroid Jelly-Fishes ' 82

Hydkoids 86

Coralline Jelly'-Fish 90

Pleurobrachia and Bougainvillea 110

European Sea- Anemones 114

Red Coral 122

Cork Polyp 128

Living Crinoids 146

Star-Fish, Holothurian, and Worms 160

Marine Worms 228

Bivalve Molluscs 276

American Land Shells 314

American Pond Snails 340

Pterotrachea 356

Musk Poulpe . . . ■ 372

Cuttle-Fish 374

THE ANIMAL KINGDOM.

INTEODUCTIOI^.

The term Natural History has at different times and by different authors been used
in a variety of senses. At the present time it is perhaps more commonly used in con-
tradistinction to natural philosophy ; it is genei-ally applied to the study of natural ob-
jects, both mineral or inorganic, and to plants and animals, or organic bodies.

At first it was applied to the study of all natural objects, whetlier the minerals,
rocks, and living beings observed upon our own planet, or heavenly bodies in general.
The study of external nature, and the phenomena or laws governing the movements of
natural bodies, was foi'inerly oijposed to metaphysics, history, literature, etc. After a
while astronomy and chemistry were eliminated from natural history ; then natui-al
philosophy, or what is now called physics, was farther sejjarated from chemistry, so
that a chemist studies the constitution or atomic nature of bodies, both inorganic and
organic ; how they combine, and how compound bodies may be analyzed or separated
into their simple constituents ; the natural philosopher, or physicist, studies the forces
of nature, the mechanical movements of inorganic bodies, and their phenomena, such
as light, heat, and electricity, while the naturalist studies minerals, rocks, plants, and
animals. But natural science, as distinguished from physical science, has made such
progress, the work has been so sub-divided or differentiated, that even the term
naturalist has become a vague, indefinite one. We must now know whether our
naturalist is a mineralogist, a geologist, a botanist, or a zoologist ; and the latter may
be an entomologist, or ichthyologist, or ornithologist, according as he devotes himself
exclusively to insects, fishes, or birds. The term natural history is popularly, at least
by many, confined to botany and zoology, often, however, to zoology alone ; and such
is the convenient though inexact title of the present work.

Man is an animal as well as a mental and spiritual being. His material body is dom-
inated by liis mind and soul, but as zoologists we study him simply as an animal. The
natural history of man is his physical history ; it concerns his bodily structure and de-
velopment, the work of his hands and the language he speaks, as well as the races into
which his species is divided.

Anthropology is a convenient and comprehensive term now generally used for the
natural history of man. The anthropologist, making a specialty of the natural history
of man, studies not only his bodily structure, especially his skull or cranium and the
other bones of the skeleton, comparing those of different races both living and extinct,
but the works of human art ; also human languages, both those now spoken and those
which have become extinct. Moreover the anthi'opologist goes out of the realm of
zoology into those of mental phenomena or psycholog}', and of sociology, and studies
man as a spirit, his notions of the future life, his myths, traditions ; he also studies his
origin, history, and social laws and government.

1

ii THE ANIMAL KINGDOM.

We have seen that tlie term natural history, as applied to plants and animals, is in-
exact, having been used in different senses ; a more exact and suitable one is Biology,
which is the science which relates to living beings. It is derived from the Greek
(J/oc, life, and Uyo:, discourse. It is divided into Botany, which relates to plants, and
Zoology (tMO)', animal; i-oyo;, discourse), the science treating of animals.

The science of zoology may be subdivided thus :

MoEPHOLOGY, or gross Anatomy, and the anatomy of the tissues

(Histology), hased on embryology.
Physiology and Psychology.
ZOOLOGY. \ Repboduction and Embkyology.

Systematic Zoology, or Classification.
Paljeontology, the study of fossil animals.
Zoo-geography, or the geographical distribution of animals.

MORPHOLOGY.

Inoeganic and Organic Bodies.

The differences between the inorganic or mineral bodies, and organic or living
bodies, are not always appreciable to the untrained eye and mind. Mineral bodies,
such as water, and solid minerals such as quartz, salt, or lime, may assume definite
crystalline shapes, and such shaj^es may grow, L e. increase in size, by the addition, on
the outside, of particles of the same substance. Minerals may exist in three different
states, gas or vapor, fluid, or solid. The air, carbonic acid gas, and water are min-
erals, as much so as lime or salt. Rocks are made up of minerals, and thus the earth,
the air, and water are of mineral origin. Minerals may assume plant-like shapes, as
seen in the beautiful forms and delicate leaf-like tracery of the frost on our windows.
The drops of sea-water dashed by the waves ujion one's coat-sleeve may be seen under a
glass to evaporate and the solid particles left to arrange themselves in beautiful but
definite crystalline forms. By watching the ev.aporation of salt water under the micro-
scope, the crystals may be seen actually to grow, i. e. to build themselves uji, to extend
and enlarge in size. "If," as Huxley states, "a crystal of common salt is hung by a
thread in a saturated solution of salt, which is exposed to the air so as to allow the
water to evaporate slowly, the molecules of the salt which is left behind and can no
longer be held in solution, deposit themselves on the crystal in regular order and in-
crease its size without changing in form. And, in this way, the small crystal may grow
to a great size." Thus growth in minerals consists in the addition of particle after
particle of solid matter to the outside of the growing body.

Now, how do living bodies essentially differ from those not living? In the first
place, plants and animals are built up of protoplasm. Protoplasm consists of mineral
matter, to be sure, but so comliined as to form a substance not found in minerals.
Moreover, a plant or animal has life ; the plant grows, and, if it is a vine, is capable of
some degree of motion, it twines about some post or tree as a sujiport ; the living bird
flies, and the living dog runs; after a time the plant or the bird dies, it is then dead.
Minerals do not die. Besides, when the plant or animal grows, it increases in size, not
like minerals, by additions from without, but by manufacturing protoplasm and other
organic substances, such as starch and fat, within its body. Thus organisms or living
beings grow by additions from within, these additions being produced by the living-
being itself. After a while this process stops and it becomes dead. As Professor Hux-

INTRODUCTION. iii

ley tells us : " In the spring, a wheat-field is covered with small green plants. These
o-row taller and taller until they attain many tnnes the size which they had when they
first appeared ; and they produce the heads of flowers which eventually change into
ears of corn.

" In so far as this is a process of growth, accompanied by the assumption of a defi-
nite form, it might be compared with the growth of a crystal of salt in brine ; but, on
closer examination, it turns out to be something very different. For the crystal of salt
o-rows by taking to itself the salt contained in the brine, which is added to its exterior ;
whereas the plant grows by addition to its interior ; and there is not a trace of the
characteristic compounds of the plant's body, albumen, gluten, starch, or cellulose, or
fat, in the soil, or in the water, or in the air.

" Yet the plant creates nothing, and therefore the matter of the proteids and amy-
loids and fats which it contains must be supplied to it, and simply manufactured, or
combined in new fashions, in the body of the plant.

"It is easy to see, in a general way, what the raw materials are which the plant
works up, for the plant gets nothing but the materials supplied to it by the atmosphere
and by the soil. The atmosphere contains oxygen and nitrogen, a little carbonic acid
gas, a minute quantity of ammoiiiacal salts, and a variable proportion of water. The
soil contains clay and sand (silica), lime, iron, potash, phosphorus, sulphur, ammoniacal
salts, and other matters which are of no imjiortance. Thus, between them, the soil
and the atmosphere contain all the elementary bodies which we find in the plant ; but
the |ilant lias to separate them and join them together afresh.

"Moreover the new matter by the addition of which the plant gi-ows is not applied
to its outer surface, but is manufactured in its interior; and the new molecules are
diffused among the old ones."

Living beings also reproduce their kind. The com bears seed, the hen lays eggs.
Minerals cannot reproduce, so that we see that organic beings differ from minerals in
three essential characteristics : they contain and are built up from protoplasm ; they
grow from within, and they reproduce by seeds, germs or eggs.

As Huxley again says : " Thus there is a very broad distinction between mineral
matter and livinsr matter. The elements of living matter are identical with those of
mineral bodies ; and the fundamental laws of matter and motion apply as much to
living matter as to mineral matter ; but every living body is, as it were, a com-
plicated piece of mechanism, which 'goes' or lives, only under certain conditions.
The germ contained in the fowl's egg requires nothing but a sujiply of warmtli within
certain narrow limits of temperature, to build the molecules of the egg into the body of
the chick. And the process of development of the egg, like that of the seed, is
neither more or less mysterious than that in virtue of which the molecules of water,
when it is cooled down to the freezing point, build themselves up into regular crystals."

The Diffkrexces between Plants and Ajstimals.

We now come to the differences between plants and animals ; and here the dis-
tinctions are more or less arbitrary. As we have remarked elsewhere, —

" It is diflicult to define wh.at an animal is as distinguished from a plant, when we
consider the simplest forms of either kingdom, for it is impossible to draw hard and
fast lines in nature. In defining the limits between the animal and vegetable king-
doms, our ordinary conception of what a plant or animal is will be of little use in
dealing with the lowest forms of either kingdom. A horse, fish, or worm differs from

iv. THE ANIMAL KINGDOM.

an elm-tree, a lily, or a fern, in having organs of sight, of hearing, of smell, of locomo-
tion, and special organs of digestion, circulation, and respiration, but these plants also
take in and absorb food, have a circulation of sap, respire through their leaves, and
some plants are mechanically sensitive, while others are endowed with motion — certain
low plants, such as diatoms, etc., having this power. In plants the assimilation of food
goes on all over the organism, the transfer of the sap is not confined to any one portion
or set of organs as such. It is always easy to distinguish one of the higher plants from
one of the higher animals. But when we descend to animals like the sea-anemones and
coral-polyps, which were called zoophytes from their general resemblance to flowers,
so striking is the external similarity between the two kinds of organisms, that the early
observers regarded them as ' animal flowers ;' and in consequence of the confused notions
originally held in regard to them, the term zoophytes has been perpetuated in works
on systematic zoology. Even at the present day the compound hydroids, such as
the Sertularia, are gathered and pressed as sea-mosses by many persons who are
unobservant of their peculiarities, and unaware of the complicated anatomy of the
little animals filling the different leaf-like cells. Sponges, until a late day, were re-
garded by our leading zoologists as plants. The most accomplished naturalists,
however, find it impossible to separate by any definite lines the lowest animals and
plants. So-called plants, as Jiacterium, and so-called animals, as Protamoeba, or
certain monads, which are simple specks of protoplasm, without genuine organs,
maybe referred to either kingdom ; and indeed, a number of naturalists — notably
Haeckel — i-elegate to a neutral kingdom (the Protista) certain lowest plants and
animals. Even the germs (zoospores) of monads and those of other flagellate infusoria,
may be mistaken for the spores of jilants; indeed the active flagellated spores of
plants were described as Infusoria by Ehrenberg ; and there are certain so-called flag-
ellate Infusoria so much like low plants (such as the red snow or JProtococcus), in
form, deportment, mode of reproduction, and a]ipearance of the spores, that even
now it is possible that certain organisms placed among them are plants. It is
only by a study of the connecting links between these lowest organisms, leading up to
what are undoubted animals or plants, that we are enabled to refer these beings to their
proper kingdom.

" As a rule, plants have no special organs of digestion or circulation, and nothing
approaching to a ner\'ous system. Most plants absorb inorganic food, such as car-
bonic acid gas, water, nitrate of ammonia, and some phosphates, silica, etc., all of these
substances being taken up in minute quantities. Low fungi live on dead animal
matter, and jjromote the process of putrefaction and decay, but the food of these
organisms is inorganic j^articles. The slime-moulds called J/yxomycetes, however,
envelop the plant or low animals, much as an Amoeba throws itself around some living
plant and absorbs its jn'otoplnsm ; but the 3fijxornycetes, in their manner of taking food,
are an exception to other moulds. The lowest animals swallow other living animals
whole or in pieces ; certain forms near Amoeba bore into minute algaj and absorb their
protoplasm ; others engulf silicious-shelled plants (diatoms and desmids) and absorb
the protoplasm filling them. No animal swallows silica, lime, ammonia, or phos-
phates as food. On the other hand, plants manufacture or produce protein in the
shape of starch, albumen, sugar, etc., which is animal food. Plants inhale carbonic
acid gas and exhale oxygen ; animals inhale oxygen and exhale carbonic acid ; though
Drajier has discovered that, under certain circumstances, plants may exhale carbonic
acid.

INTRODUCTION. V

" Animals move and have special organs of locomotion ; few plants move, though
minute forms have thread-like processes or vibratile lashes (cilia) resembling the
flagella of monads, and flowers ojjen and shut ; but these motions of the higher plants
are purely mechanical, and not performed by special organs controlled by nerves.
The mode of reproduction of plants and animals, however, is fundamentally identical,
and in this respect the two kingdoms unite more closely than in any other. Plants also,
like animals, are formed of cells, the latter in the higher forms combined into tissues.

" As the lowest plants and animals are scarcely distinguishable, it is probable that
plants and animals first appeared contempoi'aneously ; and while plants are generally
said to form the basis of animal life, this is only partially true ; a large number of
fungi are dependent on decaying animal matter; and most of the Protozoa live on
animal food, as do a large proportion of the higher animals. The two kingdoms sup-
plement each other, are mutually dependent, and probably appeared simultaneously
in the beginning of things. It should be observed, however, that the animal kingdom
overtops the vegetable kingdom, culminating in man." (Packard's Zoology.)

The Cells and Peotoplasm.

The fact that the bodies of the higher as well as of the simpler animals are com-
posed of cells was discovered by Schwann in 1839. This discovery is the foundation-
stone upon which the modern and still young science of Biology has been built. The
cell is the morphological unit of the organic world. With cells the biologist can, in
the imagination, reconstruct the vegetable and animal kingdoms. By studying the
forms and behavior of single cells and one-celled animals, such as the motions of the
Amceba., one can better understand the structure and physiology of the highest and most
specialized forms, even that of man ; for, as Geddes has remarked, " the functions of the
body are the result of the aggregate functions of its cells, and are explained by varia-
tions or phases of the activities of them."

Cells are microscopic portions of protoplasm, either with or without a wall. The
protoplasm is the most important, the dynamic part of the cell. What, then is pro-
toplasm ? As has already been said, it is the possession of this substance which dis-
tinguishes living beings from mineral. Huxley, in his " Science Primer," tells us in
simple language what protoplasm is. " If a handful of flour mixed with a little
cold water is tied ujj in a coarse cloth bag, and the bag is then put into a large vessel
of water, and well kneaded with the hands, it will become pasty, while the water
will become white. If this water is poured away into another vessel, and the knead-
ing process continued with some fresh water, the same thing will happen. But if the
operation is repeated, the paste will become more and more sticky, while the water will
be rendered less and less white, and at last will remain colorless. The sticky substance,
which is thus obtained by itself, is called gluten ; in commerce it is the substance
known as maccaroni.

" If the water in which the flour has thus been washed is allowed to stand for a few
hours, a white sediment will be found at the bottom of the vessel, while the fluid
above will be clear, and may be poured off. This white sediment consists of minute
grains of starch, each of which, examined with a microscope, will be found to have a
concentrically laminated structure. If the fluid from which the starch was deposited
is now boiled, it will become turbid, just as white of egg diluted with water does wlien
it is boiled, and eventually a whitish lumpy sulistance will collect at the bottom of the
vessel. This substance is called vegetable albumen.

vi THE ANIMAL KINGDOM.

" Besides the albumen, the ghiten, and the starch, other substances, about which
this rough method of analysis gives us no information, are contained in the wheat
grain. For example, there is woody matter or cellulose, and a certain quantity of sugar
and fat."

Similar substances are found in animals and eggs. " If you break an egg, the con-
tents flow out, and are seen to consist of the colorless glairy ' white ' and the yellow
'yolk.' If the white is collected by itself in water and tlien heated, it becomes turbid,
forming a white solid, very similar to the vegetable albumen, which is called animal
albumen.

"If the yolk is beaten up with water, no starch nor cellulose is obtained from it,
but there will be plenty of fatty and some saccharine matter, besides substances more
or less similar to albumen and gluten.

" The feathers of the fowl are chiefly composed of horn ; if they are stripped off,
and the body is boiled for a long time, the water will be found to contain a quantity
of gelatine, which sets into a jelly as it cools, and the body will fall to pieces, the bones
and the flesh separating from one another. The bones consist almost entirely of a
substance which yields gelatine when it is boiled in water, impregnated with a large
quantity of salts of lime, just as the wood of the wheat stem is impregnated ^\itli silica.
The .flesh, on the other hand, will contain albumen, and some other substances which
are very similar to allninien, termed fibrin and syntonin.

" In the living bird all these bodies are united with a great quantity of water, or
dissolved, or suspended in water ; and it must be remembered that there are sundry
otlier constituents of the fowl's body and of the egg, which are left unmentioned, as
of no present importance.

" The wheat plant contains neither horn nor gelatine, and the fowl contains neither
starch nor cellulose ; but the albumen of the plant is very similar to that of the animal,
and the fibrin and syntonin of the animal are bodies closely allied to both albumen
and gluten.

" That there is a close likeness between all these bodies is obvious from the fact
that when any of them are strongly heated or allowed to putrefy, it gives off the same
sort of disagreeable smell ; and careful chemical analysis has shown that they are, in
fact, all composed of the elements carbon, hydrogen, oxygen, and nitrogen, combined
in very nearly the same proportions. Indeed, charcoal, which is impure carbon, might
be obtained by strongly heating either a handful of corn or a piece of fowl's flesh in a
vessel from which the air is excluded so as to keep the corn or the flesh from burning.
And if the vessel were a still, so that the products of this destructive distillation, as
it is called, could be condensed and collected, we should find water and ammonia in
some shape or other in the receiver. Now ammonia is a compound of the elementary
bodies nitrogen and liydrogen ; therefore both nitrogen and hydrogen must liave been
contained in the bodies from which it is derived.

"It is certain, then, that very similar nitrogenous compounds form a large part of
the bodies of both the wheat plant and the fowl, and these bodies are called proteids.

"It is a very remarkable fact that not only are such substances as albumen, gluten,
fibrin, and syntonin known exclusively as products of animal and vegetable bodies, but
that every animal and every plant at all periods of its existence contains one or
other of them, though, in other respects, the composition of living bodies may vary
indefinitely. Thus, some plants contain neither starch nor cellulose, while these sub-
stances are found in some animals ; while many animals contain no horny matter and no

INTRODUCTION. yfi

gelatine-yielding substance. So that the matter which appears to be the essential
foundation of both the animal and the plant is the proteid united with water ; though
it is probable that, in all animals and plants, these are associated with more or less
fatty and amyloid (or starchy and saccharine) substances, and with very small quanti-
ties of certain mineral bodies, of which the most imjjortant appear to be phosphorus,
iron, lime, and potash.

" Thus there is a substance composed of water and proteids and fat and amyloids
and mineral matters, which is found in all animals and plants, and, when these are
alive, this substance is termed /)roio/)^;«^"»n."

As yet we know almost nothing of the chemical nature of animal protojilasm.
Microscopically it does not differ in appearance from vegetable protoplasm, and yet
the latter has been found by Reinke to contain over forty proximate constituents.
Hence it seems reasonable to infer that animal protoplasm will on further analysis be
found to be an exceedingly complex substance, and not properly comj^arable with a
particle of white of egg. The following account of the chemical composition of pro-
toplasm in general is from Carnoy : " Protoplasm is a complex mixture of chemical
species. The patient and minute researches of later years have resulted in the dis-
covery, in typical protoplasm of young and active cells, the following substances which
we should consider as the essential elements of the living matter :

1. Albuminoid substances (a vitelline and a myosine at minimum).

2. Phosphoric substances (lecit.hine and nucleine).

3. One or several hydrocarbonated substances (such as glyeose, dextrine, glycogene).

4. Soluble ferments (diastase, pepsine, inverslve ferment, emulsine).

5. Water (of constitution and imbibition).

6. Mineral elements (salts, sulphates, j)hosphates or nitrates of potassium, calcium,

and magnesium).

"We should also call attention to the recent analyses made by Reinke and Rode-
wald (1881) on the plasmodium of JEthaUum septicum, by which they found, besides
some accidental principles, the elements above mentioned. These analyses, as also
the microchemical researches of Zacharias (1881-83), have besides revealed to us a
new element of protean {proteique) nature, that of plastine, which seems to fill an
essential role. Finally, we may mention the researches of Mayer and Baginski, which
give a new category of soluble ferments : we refer to coagulent ferments, or presures
(Labferment). These bodies have already been verified in a quite large number of
animal and vegetable cells, which seem, like their congeners, indispensable to the
accomplishment of certain cellular phenomena."

We know that potentially the protoplasm of different kinds of cells exerts widely
different forces and capabilities. A liver cell secretes bile, a pancreas cell pancreatic
fluid, the cells lining the stomach gastric fluid, and an ovarian cell the white of an
egg. One egg-cell may become a mollusc, another a man, whose brain-cells are the
medium of the intellectual power which, enables him to write the history of his own
species, and to be the historian of the forms of life which stand below him.

The simplest, most primitive form of a cell, when without a nucleus or nucleolus,
is called a cytode. The Monera, which are the lowest animals, have no nucleus, and
have therefore been called by Hacckel cytodes. The existence of cytodes, however,
cannot yet be accej)ted as a settled fact ; all the evidence is simply negative, and forms
which once were supposed to have no nucleus (e. g. Radiolaria) have been recently

viii THE ANIMAL KINGDOM.

shown to possess such a structure. Furtlier researches may show the same to be true
of all forms and all cells.

Genuine cells have a 7iucleiis, the latter containing a ?iucleolu$. It will thus be
seen that the true cell is not a simple body; the nucleus is distinct from the rest of
the cell in structure and appearance, and the nucleolus also differs in the same way

©from the nucleus and rest of the cells. The nucleus and
nucleolus also vary in tlicmselves in size and contents, the
"^^ granules and fibres filling them varying in size and number.
" This fact should lead us to regard the cell as not so simple as
generally supposed. A recent writer, impressed by the com-
plexity of cell structure, has subjected to a critical examina-
tion the characters of ganglion cells, both smooth and striated
muscle-cells, glandular, liver, and salivary gland cells, and epi-
^mlcVeM^nrniicieoills"' thelium, both that of the mucous membrane and that which is
ciliated, as well as that of the crystalline lens, beside cartilage
and embryonic cells. Both healthy and diseased cells are found by Arnold to possess
a complicated structure. The two constituents, as ordinarily distinguished, the cell
body and the cell nucleus, consist of a ground substance as well as of granules, sets of
granules, and filaments; these latter may become very complicated in the more highly
developed forms of cells. Arnold would regard a cell as consisting of a nucleus and
of an investing mass, both of which contain, in a homogeneous ground substance,
granules and filaments.

Dr. C. S. Minot believes that the weight of an animal depends on the number and
size of its cells, and that these two variables recpiire to be determined before we can
speak definitely as to the processes of growth in animals. Minot points out that the
growth of a body is usually measured by its weight, but that this method t.akes no
account of the amount of non-protoplasmic matters present. All many-celled animals
"pass through successive cycles, in which we can distinguish the two processes of
senescence and of rejuvenation.'''' As growth is a function of rejuvenescence effected
by impregnation, it follows th.at growth can only be measured by taking into account
the number of cells living at any given time.

Animal cells are of microscopic size, but one-celled animals are in some cases large
enough to be detected with the naked eye; such are many Foraminifera, and the Sten-
tor among Infusorians. Kolliker states that the size of the cells descends on the one
hand, as in many cells — the blood cells, etc. — to 0.002-0.0003 of a line, and attains
on the other, as in the cysts of the semen and the ganglionic globules, the size of 0.02
-0.04 of a line. The largest animal cells are certain gland-cells of insects which
measure up to 0.01 of a line, and the yolk-cells or ova, especially of birds and reptiles.
Animals grow by the self-division and multiplication of cells. This is the initial,
fundamental process which underlies reproduction and growth. The cells in any part
of the growing body divide into two, and those .again sub-divide, the products of self-
division becoming as large as the original cell, and in this way the body increases in
size.

The part of the cell in which this process of self-division begins is the nucleus. A
good deal has been written upon this subject. Some .authors believe that in cell divi-
sion the nucleolus first divides, then the nucleus, and finally the cell. Prof. W. Flem-
ming, however, maintains that the nucleus first of all undergoes a change, "sejtarating
into a network of higlily refracting filaments, which take up coloring matters strongly.

INTRODUCTION.

IX

and an intermediate substance not affected by staining fluids. The nucleus network
goes through a' definite series of changes, and finally divides into two equal or sub-
equal masses, which retreat from one another, and go through, in inverse order, the
changes undergone by the mother nucleus, finally forming the nuclei of the two
daughter cells. Tlie cell-body divides after the young nuclei have separated from one
another, but before they have assumed the characteristics of quiescent nuclei." Cell
division, he adds, probably exhibits periodicity, going on vigorously at certain times,
and but little, or not at all, in the intervals.

Tissues.

Although we shall treat of the development of animals on a subsequent page of
this introduction, at the risk of repetition, we will give here an epitome of the earlier
features common to the development of all animals above the Protozoa as an introduc-
tion to the subject of tissues.

In all the animals above the Protozoa, besides reproduction by fission and bud-
ding occurring in the lower groups, there is a sexual reproduction by which one animal
or one part of an animal produces an egg, while another produces the male element or
spermatozoan. These two unite and produce the fertile egg, wliich in its turn is con-
verted into a perfect animal like the foi-m from which the genital products arose. In
only a few forms will the egg develop without an intervention of the male sexual ele-
ment, and these cases of par-
thenogenesis, so far as at {jres-
ent known, are confined to the
rotifers and arthropods.

The egg is to all intents and
purposes a simple cell, and the
processes by which it forms the
complex adult are but those of
cell-division, the resulting cells
becoming specialized, some for
the performance of one function,
some for another. In the typi-
cal form of this cell-division or
segmentation, the egg divides
first into two equal parts or cells,
each of these again into two,
producing four in all, and so on,
the regular numbers being, '2, 4,
8, 16, 32, 64, etc. This regu-
larity is but rarely perfectly car-
ried out ; the exceptional forms
will be mentioned later. The
result of this segmentation is
the production of a more or less
spherical body, which has received the name morula, from its resemblance to a mul-
berry (Fig. II. E.) Usually this morula is at first solid, but it increases in size, the
result being a hollow globe (Fig. 11.., F, surface view ; G, section), the blastula, the
vacant centre being known as the segmentation cavity. The next step is the con-

FiG. II. — Early stages ot development ot Moiioxenia: A, egg after
disappearance of the uucleus; B, egg with nucleus; C, first seg-
mentation; D, second segmentation; E, morula; F, surface view,
and G, section of blastula; H, section of early gastrula.

THE ANIMAL KINGDOM.

version of this ball with its single layer of cells into a two-layered sac. We can
now compare the egg to a hollow rubber ball. By the pushing in of one side
(ill the language of embryology, invagination) the ball can be made to resemble
the condition shown in Fig. II. H, the earliest stage of the gastrula. The single
layer of cells of the blastula is now differentiated into two layers, the outer of
which is variously termed epiblast, ectoderm or epiderm, the inner endoblast, hypoblast,
or endoderm. So far, with the modifications to be noted below, these processes are
common to all animals above the Protozoa, and with the separation into two layers
we have the essential parts of a Hijdra ; the outer layer corresponds to the skin, the
inner to the digestive tract of that sim|)le animal, as shown farther on in this volume
(p. 76.) In the higher animals — as, for instance, the frog — at one stage of the develojj-
ment these two layers alone occur, and from the outer is developed the external layer
of the skin, while the hypoblast eventually forms the lining of the central portion of
the digestive tract. We thus see that at this stage the embryo is comi^osed of skin
and stomach, and the name gastrula means a little stomach.

This epitome contains the gist of the earlier stages of a typical egg, but in nature
many variations occur, of which our space will allow but the merest mention. In eggs
which are composed of pure proto])lasm this regular development occurs, but in most
eggs another element, known as food-yolk or deutoplasm, is
present, and according to its distribution the character of
the segmentation and of the invagination varies. The pro-
toplasm is the active jjortion, the food-yolk, as the name im-
plies, is to nourish the growing embryo, and its presence
tends to retard the development of the egg. Thus, when
the protoplasm is superficial, and the food-yolk occupies a
central position, as in the crustaceans, the segmentation
jilanes .are at first confined to the surface, the central jiortion
remaining for a time unsegmonted. At otlier times the food-
yolk is confined to one pole of the e%%^ as in the frog, and
then the segmentation is, for a while at least, confined
to the protoplasmic i)ole, only affecting the other at
a comparatively late stage of development. This is
carried to its furthest extent in some of the fishes. All
of lliese modifications of the type of segmentation are
variously combined, so that great differences result, and
as in the eggs of the same class, or occasionally even of
the same genus, the distribution of the food-yolk will
vary, it will readily be seen that the segmentation is but
a very poor guide to the relationships of forms. In the
insects the segmentation is very greatly modified, but as
yet our knowledge is so slight as not to warrant any
broad generalizations on the earlier stages of the group.

Correlated with the variations in the segmentation are certain modifications in the
gastruLation and the i)rodnction of the epiblast and hy]ioblast. Let iis return to the
normal gastrula for a moment, and trace its progress just a little farther, naming some
of the points omitted above. The invagination is carried to such an extent that the
segmentation cavity is nearly obliterated, and at the same time the edges of the in-
folded ball are brought closer together, so that a comparatively narrow opening is the

Fig. III. — Segnieutiug egg of
a Crustacean (Crangon).

Fig. IV.

- Unequal segmentation
(frog).

INTRODUCTION. xi

result, known as the blastopore. This blastopore in most forms completely closes ; but
to this we will return again. The hollo\\', which we have mentioned above as foi-m-
in£j primarily the digestive cavity, is known as the archenteron or primitive stomach,
and the hypoblastic cells which form its boundary are almost invariably larger than
those of the epiblast. This is true of all gastrulas, even those where the segmentation
is regular, and the reason is not difficult to find. The external cells have to embrace a
greater superficial extent than the internal ones, and hence the layer becomes thiimer
and the resulting cells smaller. In other cases the segmentation is irregular and then
a greater inequality occurs, until in some forms the hypoblast is invaginated as a few
cells, or even a single cell, and the archenteron does not aj)pear until a later date, when
it is hollowed out of the hyj)oblastic cells. A greatly different mode of forming the
gastrula is by what is known as delamination. A general idea of the i)rocess may
be obtained by saying that the inner ends of the cells of the blastula (Fig. II., G) are
segmented off to form the hypoblast.

In the gastrula we have two of the so-called germinal layers, the epiblast and the
hypoblast; in all animals except some of the coelenterates and the Dicyemids, a third
layer, the mesoblast or mesoderm, occurs, hence these are
known as triploblastic animals, in contradistinction to those
with only hypoblast and epiblast, which are called diplo-
blastic. We will not enter into a discussion of the many
different ways in which the mesoblast arises, but will merely
indicate what is apparently the typical method, which in
reality exists umnodified in but very few animals. From
the hypoblast, pouches bud off 'on either side, as shown on
the left of our figure. These j^ouches eventually become
seiwrated from the arclienteron, as shown on the right side Fig. v.— Diagram illustrating the

/ ,1 i- ^1 1 ^1 fornKitir.li of the germ layers

01 the same figure, ami the wails ot these pouches are the (but little mociifled from that

- ■- 1 !• ,1 !• ii . occurring in P«-ijra/»a); on the

mesoblast. JNow we are ready for the names ot these parts right an earlier, on the left a

-, . (. ,-, ., ,.1,1 Ti later stage; h, blastopore; c.

and an enumeration ot the organs into which they develop. cceiom; (/. mesobiastic pouch;

. » , J. . ,. , 11. 1.1 .■ c f. epiblast; h, hypoblast; m.

Alter the lormation ot the mesolilast and the separation oi mesenteron; o,somatopiure;/j,
a portion of the archenteron, the hypoblastic cavity is t!on'cay^°yl "'*' ^' ^^^'"™ ^
known as the mesenteron, from the fact that its lining cells

form the epithelium of the middle portion of the digestive tract. From other pouches
and outgrowths of the mesenteron, formed at a later date, other organs arise. Among
these we may mention the liver, the lungs of vertebrates, the endostyle of tunicates,
jthe thyroid and thymus glands, pancreas, spleen, and the notochord.

The epiblast, as we have seen, gives rise to the outer layer of the skin. This is
not the whole of the list of its derivatives, for we must here include the nervous sys-
tem and the organs of sense, dei-mal glands, teeth, membrane-bones, etc. As we have
said, the blastopore almost always becomes completely closed, but in some forms it
remains open, forming the mouth or the vent, and in Peripatus it closes in the middle,
leaving both oral and anal openings at its extremities. In these forms where it
becomes completely closed, the mesenteron is entirely separated from the external
world, and comnuuiication has to be again opened with the exterior. This is accom-
plished by inpushings of the epil)last at the exti-emities of the body. These ingrowths
finally meet and unite with the hypoblast, and thus form the com])lete alimentary
tract. From this method of formation of the anterior and posterior parts of the
digestive canal, it follows that certain internal organs, as the oesophagus and iiites-

xii THE ANIMAL KINGDOM.

tine, the stomach of the lobster, and the gizzard of the cricket, the nialpigian tubes of
insects, etc., are really to be classed among the derivatives of the ejaiblast.

The mesoblast, after separating from the hyjjoblast, grows around between the
other two layers. It either contains a cavity, originally a part of the archenteron, or
such a cavity soon a23pears. This is the body cavity or ccelom, the pleuro-peritoneal
cavity of vertebrates. The outer wall of the coelom unites with the epiblast, the
inner with the hypoblast, and the segmentation cavity is obliterated. From the meso-
blast arise most of the structures and organs not already enumerated. The list in-
cludes the bones of vertebrates, the skeleton of echinoderms, spicules of sponges, mus-
cles, connective tissue, blood, and excretory and reproductive organs.

From an enibryological standpoint, as we have just seen, we can arrive at a classi-
fication of tissues; but if we turn to structure and function, the result is a different
association, which, for all except the pure morphologist, is far more satisfactory. The
following classification of the tissues is taken, with modifications, from Kolliker: —

1. Epithelial tissues (epidermal and glandular).

2. Co)i7iective tissues (mucous, cartilage, elastic, areolar, and osseous tissues, and
dentine).

3. Muscular tissues (smooth and striated).

4. Nerve tissue (nerve-cells and fibres).

The epithelial tissues consist of cells placed side by side, forming a layer. All the
other tissues arise from one having the cells characteristic of epithelium, as the gei-m-
layers are formed of it. As Kolliker reiterates in 1884, "In all multicellular organ-
isms all the elements and tissues arise directly from the fertilized egg-cell and the first
embryonic nucleus. (1) The tissues first differentiated have the characters of epithe-
lial tissues, and form the ectoblast and endoblast. ('!) All the other tissues arise from
these two cell-layers; they are either directly derived from them, or arise l)y the
intermediation of a median layer (mesoblast) which, when developed, takes an
important part in forming the tissues. (3) When the whole of the animal series is
considered, each of the germinal layers is found to be, in certain creatures, capable of
giving rise to at least three, and perhaps to all tissues ; the germinal layers cannot,
therefore, be regarded as histologically primitive organs."

Epithelial cells form the skin or epidermis of animals, and also the lining of the
digestive canal. The cells of the latter may, as in sponges, bear a genei-al resemblance
to a flagellate infusorian, as Codosiga, or they may each bear many hair-like processes
called cilia, which by their constant motion maintain currents of the fluids passing-
over the surface of the epithelium. The cilia lining the inside of the windpipe serve
to sweep any fluid formed there towards the throat, whei-e it can be coughed up and
expectorated.

Connective tissue and its varieties, and gristle or cartilage, bone, etc., arise from the
mesoblast and suj>port the parts of the body. All the supporting tissues are used in
the body for mechanical purposes : the bones and cartilages form the hard framework
by which softer tissues are supported and protected ; and the connective tissues, with
the various bones and cartilages, form investing membranes around different organs,
and in the form of fine network penetrate their substance and support their constit-
uent cells.

Connective tissue is formed by isolated rounded or elongated cells with wide
spaces between them filled with a gelatinous fluid or jirotoplasni, and occurs between
muscles, etc. Gelatinous tissue is a variety of connective tissue found in the umbrella

INTRODUCTION. xiii

of jelly fishes. Fibrous and elastic tissue are also varieties of connective tissue.
Cartilaginous tissue is characterized by cells situated in a still firmer intercellular sub-
stance; and when the intercellular substance becomes combined with salts of lime,
foi'ming bone, we have bony tissue.

The blood-corpuscles originate from the mesoderm as independent cells floating
in the circulating fluid, the blood cells being formed contemporaneously with the walls
of the vessels enclosing the blood. In the invertebrates the blood-cells are either
strikingly like the Amoeba in appearance, or are oval, but stOl capable of changing
their form. Thus blood-corpuscles arise like other tissues, except that they become
free.

Muscular tissue is also composed of cells, which are at first nucleated and after-
ward lose their nuclei. From being at first oval, the cells finally become elongated
and unite together to form the fibrillae ; these unite with bundles fonuing muscular
fibres, which in the vertebrates unite to form muscles. Muscular fibrilte may be sim-
ple or striated. The contractility of muscles is due to the contractility of the proto-
plasm originating in the cells forming the fibrillre.

Nervous tissue is made up of nerve-cells and fibres proceeding from them; the
former constituting the centres of nervous force, and usually massed together, forming
a ganglion or nerve-centre from which nerve-fibres pass to the periphery and extremi-
ties of the body, and serve as conductors of nerve-force. — (Packard's Zoology.)

Organs.

Animals are, with plants, called organisms, because they have organs. An organ
is any j^art of the body specially developed to perform a special kind of work. Thus
the wings are organs of flight, the heart is the organ of circulation, the leg an organ
of locomotion. The tissues we have enumerated are combined to form organs. The
simplest kind of an organ is perhaps the nucleus of the Amoeba. There are creatures
lower than the Amcvba which have no organs. These are the Monera, in which no
nucleus or any other specialized part of the body has as yet been found. If we rise
in the scale of animal life to the monad, we find that it has an external appendage or
organ like a whip-lash. In the Infusoria the body is covered with cilia, which arc the
only organs of locomotion in these animalcules. In the Hydrn, the only external organs
are the tentacles, which are situated around the head, and seem to feel for and to seize
its prey. In the higher worms we have oar-like organs of locomotion, arranged in
paii's on each side of the body ; also gills, or external breathing organs. Molluscs
have a creeping organ, the under side of the body; they also have gills and other
external parts or organs. In the crustaceans and insects the number and variety of
form of external organs, especially the legs, gills, feelers, and moutli-parts, are remark-
able, and they are highly specialized. In the vertebrates, beginning with fishes and
ending with man, we have external organs of sight, hearing, and locomotion, such as
fins, hands, and legs.

Of the internal organs of the body, the most important is the digestive cavity,
which is at first in the gastrula or early embryo of all many-celled animals, and in the
Hydra and other polyps simply a hollow in the body. As we ascend in the animal
series we can trace its gradual specialization, beginning with the lower woi'ms, and as-
cending to the annelids, also in the sea-urchin and starfish. In the molluscs, Crustacea,
and insects, as well as vertebrates, the alimentary canal is divided, during growth, into
distinct portions (i. e., the throat, stomach, and intestine), each with separate functions

xiv THE ANIMAL KINGDOM.

or uses. Early in life other organs arise as outgrowths from the digestive tract of the
embryo. These are the lungs, the livei-, jjanereas, sjjleen, etc.

There are also organs of sujiport ; such are the skeletons of animals, whether exter-
nal, as in the sea-urchin, 'starfish, lobster, or insect; or internal, as in a fish, bird, or
man. A true bony skeleton only exists in the vertebrates, or back-boned animals.

The illustrious naturalist, Cuviei-, established the principle of the correlation of
organs, showing that every organ must have close relations with the rest, and be niore
or less dependent on the others. Each organ has its particular value in the animal
economy. There is a close relation between the forms of the hard and soft parts of
the body, together with the functions they perform, and the habits of the animal.
For example, in a cat, sharp teeth for eatiug flesh, sharp curved claws for seizing
smaller animals, and great muscular activity — all coexist with a stomach fitted for the
digestion of animal ratlier than vegetable food. So in the ox, broad grinding teeth
for chewing grass ; cloven, wide-spreading hoofs, that give a broad support in soft
ground, and a four-chambered stomach, are correlated with the habits and instincts of
a ruminant. From the shape of a single tooth of an ox, deer, or a dog or eat, one can
determine not only its order, but its family or genus. Hence this prime law of com-
parative anatomy led to the establishment l)y Cuvier of the fund.amental principles of
the science of palajontology, by which the comparative anatomist can with some degree
of confidence restore from isolated teeth or bones the probable form of the original pos-
sessor. Of course, the more perfect the skeleton and teeth, the more perfect the remains
of the crust of insects or the shells of extinct molluscs, the more perfect will be our
knowledge, and the less i-oom will there be for error in restoring extinct animals.

New organs often arise by changes in the form and uses of simpler, older ones,
and the new organs m.ay l)e so much changed by the gradual modification of its func-
tions as to assume new uses. " This fact," says Gegenbaur, in the introduction to his
Elements of Comparative Anatomy, " is of considerable importance, for it helps to
explain the appearance of new organs, and obviates the difficulty raised by the doc-
trine of evolution, viz., that a new organ cannot at once appear with its function
completely developed ; that it therefore cannot serve the organism in its first stages
whilst it is gradually appearing ; and that consequently the cause for its development
can never come into operation. Every organ for which this objection has the appear-
ance of justice can be shown to have made its first appearance with a significance dif-
fering from its later function. Thus, for exanijile, the lungs of the Vertebrata did not
arise simply as a respii-atory organ, but had a predecessor among fishes breathing by
gills, in the swim-bladder, which at first had no relation to respiration. Even where
the lungs first assume the functions of a respiratory organ (Dipnoi, and many Am-
phil)ia) they are not the sole organ of the kind, but share this function with the gills.
The organ is therefore here caught, as it were, in the stage of convei'sion into a respi-
ratory organ, and connects the exclusively respiratory lungs witli the swim-bladder,
which arose as an outgrowth of the enteric tube and was adapted to a hydrostatic
function."

Org.ans may also become modified by disuse until they lose their distinctive form
and become rudimentary. Striking examples are seen in the ))arasitic Crustacea and
insects. As a result of the modification of org.ans by use and disuse, organs which are
morphologically the same become very different in function, and also in their general
appearance ; so that we may classify organs differently either by their morjihology or
physiological uses.

INTRODUCTION. XV

We speak of liiglily-develoiJed organs, and those which, are aborted, atrojjhied, or
rudimentary. Highly-developed organs are also highly specialized or differentiated ;
such organs are complicated, owing to the distinct uses or divisions of labor accorded
to each part. Thus, the eyes of worms are very simple and lowly developed com-
pared with the human eye; a fish's fin is, in part at least, morphologically the same
as the fore-leg of a cat, or the arm of a monkey or of man, but in the human arm
different nses are assigned to different portions of the limb ; it is highly developed,
specialized, or differentiated, to use terms nearly synonymous.

On the other hand, so exquisitely wrought an organ as a fish's eye may by disuse
become nearly atrophied, as in the blind fish of Maunnoth Cave, which lives in perpet-
ual darkness. And not only the eye, but the ojitic lobes and ojotic nerves may, as in the
case of a small crustacean (CecidoUea sti/r/ia), also living in Mammoth Cave, be
entirely aborted. Among reptiles are some extraordinary cases of modification by
degeneration and atrophy. Tlie lizard-like creature, Seps, has remarkably small limbs,
and in Bipes there is only a pair of stumps, representing the hinder limbs. As Lan-
kester claims, these two forms represent two stages of degeneration or atrophy of the
limbs ; " they have, in fact, been derived from the five-toed, four-legged ordinary lizard
form, and have nearly or almost lost the legs once possessed by their ancestors." The
entire order of snakes is an exam])le how the loss, by atrophy, of the limbs may become
common to an entire group of animals numbering thousands of species ; the possession
by the boas of a rudimentary pelvis, and minute but nearly atrophied hind legs, tends
to prove that all the snakes are descendants from some ancestral form whose limbs
became lost through disuse.

Among the Diptera, which have but a single pair of wings, there is an universal
atrophy of the second or hinder pair of wings ; moreover, there are numerous wing-
less, degraded forms, and when we take into account the fact that almost all dipterous
larvffi are nearly headless and evidently degenerated forms, we are inclined to think
that the entire group of true flies, numbering at least twenty thousand sjjecies, are
the result of a retrograde development, affecting in every species the hinder pair of
wings, and in numerous other forms the mouth-parts and other portions of the body,
both in the larval and adult states. The gi-ou]:> of barnacles (Cirripedia) is another
example where atrojihy and degeneration ])ervade each member of an order, and the
cases are highly interesting and suggestive.

An entire sub-kingdom of animals may be degenerated in some respects. Such is
the branch or sub-kingdom of sjjonges ; the adult forms of which, l)y becoming fixed,
have undergone a retrograde development, the gastrula or lar\al forms showing a
promise of a state of development which the organism not only does not attain,
but from which it falls completely away in after life. Lankester regards the acepha-
lous molluscs, or bivalves, as having degenerated from a higher type of head-bearing
active creatures like the snails. The aseidians start in the same path of development
as the vertebrates, and at length fall back and lose nearly every trace of a vertelirate
alliance.

Besides sub-kingdoms, classes, and orders of animals, we have minor groups which
are in their entirety examples of a backward development. Without doubt certain
human races, as the present descendants of the Indians of Central America, the mod-
ern Egyptians, " the heirs of the great Oriental monarchies of pre-Christian times," the
Fuegians, the Bushmen, and even the Australians, may be degenerate races. Lankes-
ter, in his book on " Degeneration," considers the causes of retrograde development

xvi THE ANIMAL KINGDOM.

to be due to — 1, parasitism ; 2, fixity or immobility of the animal ; 3, vegetative
nutrition, and 4, excessive reduction in the size of the body.

Analogy and Homology.

When we compare the wing of an insect with that of a bird, and see that they are
put to the same use, we say that they are analogous ; for when we carefully compare
the two organs, we see how unlike throughout they are. When we compare the fin
of a whale with the fore-leg of a dog or bear, we see that one is adapted for swimming,
and the other for running on dry land ; but, however unlike the two limbs are superfi-
cially, we find, on dissection, that all the principal bones and muscles, nerves and blood-
vessels of the one correspond to those in the other, so that we say there is a structu-
ral resemblance between the two kinds of limbs. Thus analogy implies a dissimilarity
of structure in two organs, with identity in use, while homology implies blood-relation-
ship. Analogy repudiates any common origin of the organs, however physiologically
alike.

In the early days of zoological science, but little was said about homologies ; but
when comparative anatomy engaged the attention of philosophical students, attention
was given to tracing the resemblances between organs superficially and functionally
unlike. It was found that the world of life teemed with examjjles of homologous
parts.

Afterwards, when the theory of evolution became the most useful tool the compar-
ative anatomist could wield, and when the knowledge of comparative embryology
completed his equipment, the most unexpected homologies were discovered. Of
course, the more nearly related are the two animals possessing homologous organs,
as the dog and whale, the closer and more jilainly homologous are their fore limbs.
It is easy to trace the homologous organs in animals of the same order or class,
however effectually degeneration on the one hand, or differentiation on the other,
have done their work.

But it was then found that the branchial sacs of ascidians are homologous with
the pharyngeal chamber of the lamprey eel ; that the position of the nervous system
in ascidians accords morjjhologically with that of fishes and higher verteljrates ; that
the notocord of larval ascidians is the homologue of that of the lancelet and lam-
prey, as well as that of embryo vertebrates in general ; and, finally, the homologies
between the laiwal ascidians and vertebrates are so startling that many comparative
anatomists now maintain that the ascidians belong, with the vertebrates, to a common
branch of the animal kingdom called Chordata. On the other hand, excellent anato-
mists trace homologies between certain organs in worms, and corresponding organs
in sharks and other vertebrates ; the segmental organs of worms have their homologous
parts in the urogenital organs of sharks ; the worm Balanoglossus has a respiratory
chamber homologous with that of the lancelet and lamprey. Hence it came to pass
that these general homologies between the lower, less specialized classes of inverte-
brates, ]iarticularly the worms, and the lower vertebrates, were so many proofs of the
origin of the latter from worms or worm-like forms. Hence the opinion now preva-
lent that a homology between organs, however unlike in the uses at present made of
them, implies that the anhnals having such organs had a common ancestry. Hence,
also, the proofs of the unity of organization of the animal kingdom are based on a
profound study of the resemblances in the tissues and organs of animals, rather than
of their superficial, recently-acquired differences.

INTRODUCTION. xvii

Homology may be general or special; the latter limited, for the most part, to
animals of the same sub-kingdom. It is well to use words which will express our
meaning exactly, and hence a general homology may be indicated by the word
isogeny, indicating a general similarity of origin ; thus, the nervous system of
Avorms, arthropods, molluscs, and vertebrates are isogenous, all being derivations
of the epiblast. The term liomology should be restncted to those cases where the
correspondence, part for part, is more exact. Thus, the brain of fishes and that of
man are not only isogenous, but homologous.

The Scale of Peefectiox in Organs and in Animals.
The history of the rise and progress of the human arm, possibly, as some claim,
from an organ like the tin of a shark, a boneless, flabby limb; how it gradually, by
adaptation, became like the differentiated fore-leg of a salamander, then became adaj^ted
for a climbing, arboreal use, and finally became, next to his brain, the most distinctive
organ in man, — the history of the successive steps in this rise in the scale of pei-fec-
tion would throw light on the general subject of the gradual perfection of organs and
organisms. On the other hand, the hinder extremities or legs of man have not been
equally perfected. As Cope has remarked : " He is plantigrade, has five toes, separate
carpals and tarsals, a short heel, rather flat astragalus, and neither hoofs nor claws, but
something between the two." Man's limbs are not so extremely specialized as those
of the horse, which is digitigrade, walking only on four toes, one to each foot. Man's
stomach is simple, not four-chambered, as in the ox. Thus one organ, or one set of
organs, may in man attain the highest grade in the scale of perfection, while others
maybe comparatively low in form and function. Animals acquire, so to speak, their
form by the acceleration in the growth of certain parts, which involves a retardation
in the development of others ; it is by the unequal development of the different parts
that the fish has become adapted to its life in the water, that the bird becomes fitted
for its aerial existence, and that moles can burrow, and monkeys are enabled to climb.'
The scale of perfection, as applied to organs, is a relative one ; those in each animal
are most perfect which are best adapted to subserve the requirements of that creature.
Man's brain is on the whole the most perfect of all oi-gans, and it enables him to regu-
late the movements of his limbs and other organs in a manner alone characteristic of
an intellectual, reasoning, speaking, spiritual being.

Generalized and Specialized Types.
A large proportion of the higher classes of animals now living are more or less
specialized ; they stand at or near the head of a series of forms which have become
extinct, and which were much less specialized. For example, there are now living
nearly ten thousand species of bony fishes, while the remains of only about twenty
species have been found in the cretaceous formation. The earlier types of fishes were
generalized or composite in their structure, ]iresenting, besides the cartilaginous
skeleton, a feature occurring in the embryos of lung fishes, characteristics which place
them above the bony fishes. Among fishes, the lung fishes or Dipnoi, are the clearest
example of a generalized type ; they have a notocord, in which respect they resemble
the lancelet and lamprey ; while they possess one or two lungs, in which respect they
resemble the salamanders or batrachians ; thus in some features they ai-e lower, and
in others higher, than any of the bony fishes. There is a strange mixture of characters
in these composite animals, and the living forms may be regarded as old-fashioned.

xviii THE ANIMAL KINGDOM.

archaic types, the survivors of a large gi'oup of Devonian forms. They were called
by Agassiz prophetic types, as they pointed to the coining of more highly wrought,
specialized forms, the amphibians. They are now regarded as ancestral forms from
which have originated two lines of organisms, one culminating in the bony fishes, and
the other in the labyrinthodonts and salamanders and other batrachians.

The king or horse-shoe crab {Limulus) is likewise a composite, synthetic, compre-
hensive or generalized type, as it is variously called. Its development and structure
shows certain features closely resembling the Arachnida, while it is also closely allied
by other points to the Crustacea, with other features peculiar to itself. Its position in
the scheme of nature is now in dispute, owing to the admixture of characters in
which it resembles both the Crustacea and Arachnida. Now Limulus is a survivor or
remnant of a long line of forms which flourished in the paljeozoic seas, at a time when
there were no genuine Crustacea nor Arachnida, which did not arise until long after
the Merostomata {Eurypterus, etc.) and their allies, the trilobites, began to disappear.
These generalized, composite arthropods lived, had their day, and finally gave way to
the hosts of highly specialized modern Crustacea, such as the shrimps and crabs of our
seas, and to the scorpions and spiders inhabiting the land, and which owe their diver-
sity of form to the highly wrought structure of a few special parts.

So, among insects, the earlier were the more generalized, old-fashioned forms. Such
were the white ants, cockroaches, grasshoppers, may-flies and dragon-flies, the earliest
insects known. Their numbers are scanty at the present day. They have been in
part supplanted by the thousands of species of beetles, moths, butterflies, ants, wasps,
and bees, so characteristic of the present age of the world as compared with the insect
life of the carboniferous period.

Among mammals the horse is the most sj^ecialized ; its generalized ancestors were
the Coryphodon and Eohippns. The latter had four usable toes, and the rudiments
of a fifth on each forefoot, and three toes behind. The history of the horse family is
a record of successive steps by which a highly specialized type was produced, culmina-
ting in that extreme form, the American trotting horse, which can only do one thing
well, i. e. excel in trotting over a racecourse.

PHYSIOLOGY.

The most difiicult line of study in biology is to determine how the organs do their
work. This is the ofiice of the physiologist. It is comparatively easy to discover how
a fish uses its fins in swimming, how a mammal walks, how a bird flies ; but it is diffi-
cult to ascertain how the internal organs perform their functions; how the stomach
digests food, exactly what ofiice the biliary and pancreatic fluids fill in the compli-
cated process of digestion ; the function of the spleen, and so on with the other viscera.
Here, besides observation and comparison, the physiologist has to rely on experiments
to test the results of his observations. The pathway to a complete understanding of
human physiology lies through the broad and as yet only partially surveyed field
of animal physiology. We can better understand the physiology of digestion in man
by studying the process of intracellular digestion in the Infusoria, the sponges, and
jelly-fish, where, owing to the transparency of the tissues, the process can be actually
observed ; so likewise, the nature of muscular movements can best be understood by
observing under the microscope the contractility of the protoplasm of individual
cells or one-celled organisms. The physiology of reproduction could never have been

INTRODUCTION.

XIX

understood without a study of the operations of cell-division, self-fission and gemma-
tion in the one-celled animals and polyps. Our most eminent human physiologists,
such as Remak, Bischoff, von Baer, and others, have had to go to the lower animals for
facts to illustrate the reproductive processes in man. No medical student can in these
days afford to be ignorant of the general laws of animal physiology.

Locomotion.

All the movements of the body, or of the internal organs, with which physiology
has to do, depend primarily on the contractility inherent in the protoplasm filling
the cells of the body. Of the cause of contractility in protoplasm we know nothing.
We see its manifestations in the irritability and resulting contractions of the body of
the Amoeba, of the white blood-corpuscle, and other cells and one-celled organisms.
It is this inhei'ent contractility of the protoplasm in muscle-cells which gives rise to
muscular movements.

But the simplest one-celled animals do not move about by means of muscles. The
Amoeba changes its position, Proteus-like, by variously contracting the body, and thus
changing its form, throwing out root-like processes in different directions. The
Infusoria have permanent thread-like processes, called cilia, by which they can swim
about in the water. In the Hijdra and other polyps, however, we meet with muscles,
by which the body can contract in certain parts; in such animals the base of the body
forms a more or less contractile, movable, creeping disc, while the tentacles move
partly by means of their muscular walls, and partly mechanically by filling them with
the circulatory fluid of the body.

The sea-urchin and starfish move slowly over the sea weed and rocks by means
of long, slender suckers. Extending these by allowing the water to flow into them,
and fastening them to the surface of the object over which they are moving, they then
contract them, and in this way the body is warped slowly along.

In the lower worms, such as the flat-worms, or in the snails, the gliding movement is
due to the mugcular contractions of the under side of the body. The gliding motion
of snails is due to a system of extensive muscular fibres within the disc, which act
when the sinuses within the disc are filled with blood ; their extension causing the
undulating appearance on the under side of the snail's foot, or creeping disc; but
the snail can only thus move forwards; the lateral movements and shortening of
the foot being produced by oblique muscular fibres.

Rising in the zoological scale, we come to the Crustacea and insects which have
jointed legs, ending, in the latter, in claws adapting the limb both for walking and
climbing. The legs of arthropods are perhaps modifications of the lateral fleshy
oar-like appendages of the sea-worms, which have become externally hard and jointed,
with several leverage-systems. The mechanism of locomotion is fundamentally the
same in the legs of arthropods and vertebrates. Space does not permit us to discuss
the subject of the mechanism of walking, running, and flying, but all these movements
are dependent primarily on the contractility inherent in the protoplasm filling the cells
forming muscular tissue.

Digestion.
The most important organs in the animal system are those relating to digestion, as
an animal may respire solely through its body-walls, or do without a circulatory or
nervous system, but must eat in order to live and grow. The opening by which the

XX THE ANIMAL KINGDOM.

food is taken into the alimentary canal is called the mouth, wliether reference is made
to the ' mouth ' of a liydra or of a vertebrate. Although the structure of the edges
may differ radically, still in most Metazoa the mouth is due to an inpushing of the ec-
toderm, however differently the edge may be supjiorted and elaborated. The edges
of the mouth are usually called the lips, but true lij^s for the first time appear in the
Mammalia. The trituration or mastication of the food is accomplished among the in-
vertebrates in a variety of ways, and by organs not always truly homologous.

The object of digestion is to reduce the food into a convenient condition, and to
dissolve or to transform it into tissue-food. How the products of digestion are carried
about in the body, so as to sup]ily the tissues of the various organs, by the circulatory
organs, will be pointed out in the next section. The simplest form of the digestive
process may be seen by a skilled observer in the cells lining the digestive jiockets or
chambers in the interior of a sponge or jelly-fish. Each cell has a certain amount of
individuality, taking in, through transitory openings in their walls, particles of food, and
rejecting the waste portions, much as individual Infusoria, which have no stomachs, in-
gest their food, and reject the particles which are indigestible or not needed. Not only
has intra-cellular digestion, as it is called, been observed in sponges and jelly-fishes, as
well as in ctenophores, but also in low worms (Turbellaria).

We will now look at the leading steps in the evolution and s])ecialization of the di-
gestive cavity of animals. In the polyps, such as Hydra and Coryne, it is simply a
hollow in the bodj'. The Hydra draws some little creature with its tentacles into its
stomach ; there it is acted upon by the juices secreted by the walls of the stomach, and
the hard parts rejected from the mouth. For the technical name of tlje digestive tract
as a whole, we may adopt Hacckel's term enteron.

In the jelly-fishes the stomach opens into four or more water-vascular canals or
passages, by which the food, when partially digested and mixed with sea-water, thus
forming a rude sort of blood, supplies the tissues with nourishment. In the sea-anem-
ones and coral polyps, the digestive cavity is still more specialized, and its walls are
partly separated from the walls of the body, though at the j^osterior end the stomach
opens directly into the body cavity. In the echinoderms and worms do we find for
the first time a genuine digestive tube, lying in the perivisceral space (which, with
Haeckel, we may call the ccelom), and opening externally for the rejection of waste
matter.

In the worms the digestive canal becomes separated into a mouth, an oesophagus,
with salivary glands opening into the mouth, and there is a division of the diges-
tive tract into three regions — i.e., fore (oesophagus), middle (chyle-stomach), .and
hind enteron (intestine). In the molluscs and higher worms there is a well-marked
sac-like stomach and an intestine, with a liver, present in certain worms and in the ascid-
ians and molluscs, opening into the beginning of the intestine. All these divisions of
the digestive tract exist still more clearly in the Crustacea and most insects. In the
latter, six or more excretory tubes (Mal]iigian vessels) discharge their contents into
the intestines, and in the ' respiratory tree ' of the Holothurian, and the segmental
organs of certain worms we have organs with probably similar excretory uses.

In the vertebrates, from the lancelet to man, the alimentary canal has, without
exception, the three divisions of oesophagus, stomach, and intestine, with a liver. In
this branch the lungs ai-e modified parts of originally sac-like dilatations of the first divi-
sion of the digestive tract. The intestine is also sub-divided in the mammals into the
small and large intestine and rectum, a coecum being situated at the limits between the

INTRODUCTION. Xxi

small aud large intestine. We thus observe a gradual advance in the degree of spe-
cialization of the digestive organs, corresponding to the degree of complication of the
animal. — (Packard's Zoology.)

We will now look at the glands which pour their secretion into the digestive canal.
In the worms, salivary glands send their secretion into the throat, while in the polyps
(ccelenterates) and many worms, and in all insects the stomach is lined with a layer of
colored cells which secrete bile ; in the spiders the stomach forms a set of complicated
ccecal appendages which secrete a fluid like bile ; in the Crustacea, and lower molluscs,
there is a liver formed of little glamls which open into the beginning of the intestine,
while in the higher molluscs and in the vertebrates we have a true specialized liver
merely connected with the digestive canal by its ducts.

Thus the original food-stuff is variously treated by animals of different grades.
In the sea-anemone or any polyj), a very imperfectly digested material is pro-
duced, which is taken at first hand, mixed with the sea-water, and in part churned by the
movements of the body, in part moved about in a more orderly and thorough manner,
in currents formed by the cilia lining the chambers of the body.

In the worms, and insects, etc., the chyle or products of digestion percolates, or
oozes through the walls of the intestine into the body cavity, and there directly mingles
with the blood, and is thus carried in the circulation to every part of the body, however
remote or minute. In the vertebrates, however, this is not so. The chyle, a much
more elaborate fluid than that of the lower animals, is carried by an intricate system
of vessels, called lymphatics, from the intestine to the blood vessels. Thus the process
of digestion becomes increasingly elaborate as we ascend in the animal series, and as
the digestive system becomes more and more complex.

Here again we might look at the chewing apparatus or teeth, arming the mouth, by
wiiich the food is made ready for digestion. To quote from the author's text-book of
Zoology: — Hard bodies serving as teeth occur for the first time in the animal series in
the sea-urchins, where a definite set of calcareous dental processes or teeth, with solid
supports and a complicated muscular apparatus, serves for the comminution of the food,
which consists of decaying animals and sea-weeds. In those echinoderms which do
not have a solid framework of teeth, the food consists of minute forms of life, proto-
zoans and higher soft-bodied animals, or the free-moving young of higher animals,
which are carried into the niouth in currents of water or swallowed bodily with sand
or mud.

Among the worms, true organs of mastication for the first time appear in the
Rotatoria, where the food, such as Infusoria, etc., is crushed and is partly comminuted
by the well-marked horny and chitinous pieces attached to the mastax. In most other
low worms the mouth is unarmed. In the leeches there are three, usually in the
annelids two, denticulated or serrate, chitinous flattened bodies, situated in the exten-
sible pharynx of these worms, and suited for seizing and cutting or crushing their
prey.

In the higher molluscs, such as the snails (Cephalophora) and cuttles, besides
one or more broad, thin pharyngeal jaws, comparable with those mentioned as existing
in the worms, is the lingual ribljon, admirably adapted for sawing or slicing sea-weeds,
and cutting and boring into hard shells, acting somewhat like a lapidary's wheel ; this
organ, however, is limited in its action, and in the cuttles, the jaws, which are like a
parrot's beak, do the work of tearing and biting the animals serving as food, which are
seized and held in place by the suckered arms.

xxii THE ANIMAL KINGDOM.

In the crustaceans and insects we have an approach to true jaws, but here they
work hiterally, not up and down, or vertically, as in the vertebrate jaws ; the mandi-
bles of these animals are modified feet, and the teeth on their edges are simply
irregularities or sharp processes, adapting the mandibles for tearing and comniiuutino-
the food. It is generally stated that the numerous teeth lining the crop of Crustacea
and insects, serve to further comminute the food after being partially crushed by the
mandibles, but it is now supposed that these numerous points also act collectively as a
strainer to keep the larger particles of food from passing into the chyle-stomach until
finely crushed.

The king-crab burrows in the mud for worms (Nereids, etc.) ; these may be found
almost entire in the intestine, having only been torn here and there, and partly crushed
by the spines of the base of the foot-jaws, which thus serve the purpose effected by
the serrated edges of the mandibles of the genuine Crustacea and insects. ,

Among vertebrates the lancelot is no better off than the majority of the coelen-
terates and worms, having no solid parts for mastication ; and the jaws and teeth of
the hag-fish, and even the lamprey eel, form a very different apparatus from the jaws
and its skeleton in the higher vertebrates ; and even in the latter the bony elements
differ essentially in form in the different classes, though originating in the same man-
ner in embryonic life. In the birds, the jaw-bones are encased in horny plates; true
teeth being absent in the living species, the gizzard being, however, provided with
two hard grinding surfaces; on the other hand, mammals without teeth are excep-
tional.

The teeth of fishes are developed, not only in the jaws, but on the different bones
projecting from the sides and roof of the mouth, and extend into the throat. In
many cases, in the bony fishes, these sharp recurved teeth serve to prevent the prey,
such as smaller fish, from slipping out of the mouth. On the other hand, the upper
and lower sides of the mouth of certain rays {3fijliobatis) are like tlie solid pavement
of a street, and act as an upper and nether mill-stone to crush solid shells.

In the toothless ant-eaters the food consists of insects, which are swallowed with-
out being crushed in the mouth ; true teeth are wanting in the duck-bill, then- place
being taken by the horny processes of the jaws, while in Steller's manatee the
toothless jaws were provided with horny solid plates for crushing the leaves of succu-
lent aquatic plants. Exam])les of the most highly differentiated teeth in vertebrates are
seen in those animals which, like the bear, are omnivorous, feeding on flesh, insects, and
berries, and which have the orown of the molars tuberculate ; while the canines are
adapted for holding the prey firmly as well as for tearing the flesh, and the incisors
for both cutting and tearing the food.

Circulation.
Intimately associated with the digestive canal are the vessels in which the pro-
ducts of digestion mix with the blood and supply nourishment for the tissues, or, in
other words, for the growth of the body. In the Infusoria the evident use of the con-
tractile vesicles is to aid in the diffusion of the partly digested food of these micro-
scopic forms. In the Hydra the food stuff is directly taken up by the cells lining the
coelom, while the imperfectly formed blood also finds access to the hollows of the
tentacles. The mode in which the cells lining the canals in the sponge take up, by
means of pscudopodia, microscopic particles of food, directly absorbing them in their
substance, is an interesting example of the mode of nourishment' of the cellular tissues

INTRODUCTION. xxiii

of tlie lower animals. The sea-rinemone presents a step in advance in organs of circu-
lation ; here the partly digested food escapes through the open end of the stomach
into the perivisceral chambers formed by the numerous septa, the contractions of the
body churning the blood, consisting of sea-water and the particles of digested food,
and a few blood-corpuscles, hither and thither, and with the cilia forcing it into every
interstice of the body, so that the tissues are everywhere supplied with food.

The water-vascular system of the ccelenterates presents an additional step in de-
gree of complexity ; but it is not until we reach the echinoderms, on the one hand,
and such worms as the Nemertes and its allies on the other, where deiinite tubes or
canals, the larger ones contractile, and, in the latter type at least, formed from the
mesoderm, serve to convey a true blood to the various parts of the bodj', that we have
a definite blood system. In the echinoderms a true hasmal or vascular system may co-
exist with the water-vascular system. In the annelids, such as the Nereis, one of the
blood-vessels may be modified to form a pulsating tube or heart, by which the blood
is directly forced outward to the periphery of the body through vessels which may, by
courtesy, be called arteries, while the blood returns to the heart by so-called veins.

The molluscs have a circulatory system which presents a nearer approach to the
vertebrate heart and its vessels than even in the crustaceans and insects, for the ven-
tricle and one or two auricles, with the complicated arterial and venous system of
vessels of the clam, snail, and cuttle-fish, truly foreshadow the genuine heart and sys-
temic and pulmonary circulation of the vertebrates. The molluscs, and king-crab, and
the lobster, jiossess minute blood vessels which present some approach to the capillaries
of vertebrates. The circulation in certain worms, from Nemertes upward, may be said
to be closed, the vessels being continuous ; but they are not so in insects where true
veins are not to be found, the blood returning to the heart in chainiels or lacunre in
the spaces between the muscles and viscera.

In vertebrates the ' aortic heart ' of the lancelet or Amphioxus is simply a pulsat-
ing tube, and there are portions of other vessels which are pulsatile, so that there is,
as in some worms, a system of ' hearts.' A genuine heart, consisting of an auricle and
a ventricle only, first ajjpears in the lamprey. This condition of things survives in
fishes, with the exception of those forms, such as the limg-fish (Dipnoans), whose
heart anticipates in structure that of the amphibians and reptiles, in which a second
auricle appears. Again, certain rejjtiles, such as the crocodiles, anticipate the birds
and mammals in having two ventricles — i. e., a four-chambered heart. It should be
borne in mind that in early life the heart of all skulled vertebrates (Craniota) is a
simple tube, and as Gegenbaur states, " as it gradually gets longer than the space set
apart for it, it is arranged in an S-shaped loop, and so takes on the form which the
heart has later on." Owing to this change of form it is divided into two parts, the
auricle and ventricle.

A striking feature first encountered in the craniate vertebrates is the presence of a
set of vessels conveying the nutrient fluid or chyle which filters through the walls of the
digestive canal to the blood-vessels ; these are, as already stated, the lymphatics. In
the lancelet, as well as in the invertebr.ate animals, such vessels do not occur, but the
chyle oozes through thf" stomach-w.alls and directly mixes with the blood.

Rbspikation.
Always in intimate relation with the circulatory system are the means of respira-
tion. The process may be carried on .all over the body in the simple animals, such

xxiv THE ANIMAL KINGDOM.

as Protozoa or sponges, or, as in ccelenterates, it may be carried on in the water-
vascular tubes of those animals, while in the so-called respiratory tree of echin-
oderms it may go on in company with the performance of other functions by the same
vessels. Respiration, however, is inclined to be more active in such finely subdivided
parts of the body as the tentacles of polyps, of worms, or any filamentous subdivisions
of any of the invertebrates; these parts, usually called gills, present in the aggregate a
broad resjjiratory surface. Into the hollows of these filamentous ijrocesses, which are
usually extensions of the body-walls, blood is driven through vessels, and the oxygen
in the water bathing the gills filters through the integument, and immediately gains
access to and mixes with the blood. The gills of the lower animals appear at first
sight as if distributed over the body in a wanton manner, appearing in some species on
the head, in others along the sides of the body, or in others on the tail .alone ; but in
fact they always arise in such situations as are best adapted to tlie mode of life of the
creature.

The gills of many of the lower animals afford an admirable instance of the econ-
omy of nature. Tlie tentacles of polyps, pohzoans, brachiopods, and many true worms
serve also, as delicate tactile org.ans, for grasping and conveying food to the mouth,
and often for locomotion. The suckers or 'feet' of star-fish or sea-urchins also without
doubt help to perform the office of gills, for the luxuriously branched, beautifully-col-
ored tentacles of the sea-cucumber are simply modifications of the ambulacral feet.

In the molluscs, especially the snails and cuttle-fish, the gills are in close relations
with the heart, so that in tlie cuttle-fish the auricles are called ' branchial hearts.' The
gills of crustaceans are attached either to the thoracic legs or are modified abdominal
feet, being broad, thin, leaf-like processes into which the blood is forced by the con-
tractions of the tubular heart. Respiration in the insects goes on all over the interior
of the body, the tracheal tubes distributing the air so that the blood becomes oxyge-
nated in every part of the body, including the ends of all the appendages. The gills
of aquatic insects are in all cases filamentous or leaf-like expansions of the skin permea-
ted by tracheae; they are, therefore, not strictly homologous with the gills of crust.a-
ceans or of worms. — (Packard's Zoology.)

We now come to the respiratory organs of the vertebrates, which are in close rela-
tion to the digestive canal. First the gills : just behind the mouth are openings, called
branchial clefts, on the edges of which arise processes, the gills or branchiae. Through-
out these gills are distributed minute arteries and veins, forming a.network ; the gills
are bathed in water taken in through the mouth. In the amphibians and lung-fishes,
(Dipnoi) lungs, which are outgrowtlis of the enteric canal, replace the swimming
bladder of the fishes, the air being now swallowed by the mouth and gaining access by
a special pass.age, the larynx, to highly specialized organs of res]uration, the lungs,
which are situated in the thoracic cavity near the heart.

Neeves and Sensation.
We have seen that animals of comparatively complicated structure perform their
work in the anim.al economy without any nervous system whatever. In none of the
Protozoans, even the highest infusorians, have true nerve-cells been yet detected ; in
these animals the tissues are in an inchoate, non-specialized state. It is not until we
rise to the many-celled animals that we observe nerves and nerve-centres. It has been
only recently discovered that in many jelly-fish there is, for the first time in the ani-
mal series, a true nervous svstem, with definite nerve-centres or ganglia. In the

INTRODUCTION. XXV

hydroids none has been found, so that the majority, if not all, of the polyps jDcr-
form their complicated movements, capturing and taking in food, digesting it, and
reproducing their kind, without the aid of what seems, when we study vertebrates
alone, as the most important and fundamental system of organs in the body.

The Protozoa, sponges, and many coelenterates depend, for the power of motion,
on the irritability and contractility of the protoplasm of the body, whether or not
separated into muscular tissue. Referring to the complicated moveuients of the Pro-
tozoa, Dr. Krukenberg well says: "The changeful phenomena of life, which we
reinark in the smallest organisms — in the rhythm of their ciliary motions, now
sti-engthened, now slackened; in the rhythmic alternation of the capacity of their
contractile vesicles; in their regulated incomes, deposits, and expenditure; in the
abundance of the visible products of their diverse material exchanges — enable us but
remotely to foresee what is here effected by a harmonious co-operation of countless
processes limited to the smallest space. Let their formal differentiation seem to us
ever so slight, just so do these beings become for us all the greater riddles, especially
when we find in them vital manifestations elsewhere displayed in the living world
only by apparatus of the most highly complex constructions, and in them meet with
processes which, without the orderly co-operation of very different factors, must
remain to us unintelligible." In the Hydra for the first time appear the traces of a
nervous tissue in the so-called neuro-muscular cells, one portion of a cell being muscu-
lar, the other nervous in its functions.

A more definite nervous organization has been detected in the Actinire, iu the
form of disconnected bodies and rod-like nerve cells, and other nervous bodies found
near the eye-spots, and the nerve-cells and fibres at the base of the body ; but a
genuine nervous system for the first time appears in certain naked-eyed jelly-fishes, in
which it is circular, sharing the radiated disposition of parts in these animals. As the
results of his experiments on the ctenophores, Krukenberg finds that animals of this
cjass, of comparatively simple structure, and therefore exhibiting morphological differ-
ences wliich to us seem trifling, may nevertheless display very diverse reactions when
exjDosed to similar abnormal conditions in the physiological laboratory. " In our
attempt to explain the occult vital powers thus revealed, we are debarred from an
appeal to the apparently corresponding diversities sometimes encountered in the case
of the much more complex vertebrates." The echinoderms have a well-develoi3ed
nervous system, consisting of a ring (without, however, definite ganglia, though
masses of ganglionic cells are situated in the larger nerves), surrounding the (esopha-
gus, and sending a nerve into each arm ; or, in the holothurians, situated under the
longitudinal muscles radiating from that muscle closing the mouth. Recent researches
on the star-fish show, however, that besides the ring around the mouth, and the five
main nerves passing along the arms or rays, there is a thin nerve-sheath which encloses
the whole body, and is directly continuous with the external epidermis, of which it
forms the deepest layer. The circumoral and radial nerves are believed to be simply
thickenings of this thin nervous sheet.

In this connection should be mentioned the experiments made by Romanes, Ewart,
and Marshall, on living Echini, " which lead them to believe in the existence not only
of an external nerve-plexus outside the test, but also of an internal plexus on its inner
surface ; they further believe that the two systems are connected by nerve-fibres run-
ning through the ])lates of the test or shell."

In all other invertebrate animals, fi'oni the worms and Mollusca to the crustaceans

xxvi THE ANIMAL KINGDOM. ■

and insects, the nervous system is fundamentally built nearly upon the same plan.
There is a pair of ganglia above the oesopliagus, called the 'brain;' on the under side is
usually a second pair; the four, with the nerves or commissures connecting them, form-
ing a ring. This arrangement of ganglia, often called the ' oesophageal ring,' consti-
tutes, with the slender nerve-threads leading away from them, the nervous system of
the lower worms, in many of which, however, as also in most Polyzoa and Brachio-
poda, the suboesophageal ganglia are wanting. Now to the oesophageal ring with its
two pairs of ganglia, add a third pair, the visceral ganglia, and we have the nervous
system of the clam and many molluscs.

In the higher ringed worms, the Annulata, and in the Crustacea and Insects, thei-e
is a chain of ganglia, or brains, which, behind the throat, are ventral, and lie on the
floor of the coeloni or body cavity. The highest form of nerve-centre found in the
invertebrate animals, and which hints at the brain and skull of vertebrates, is the
mass of ganglia partly enclosed in an imperfect cartilaginous capsule in the head of
the cephalojiods. The nervous cord of the Ajjpendicularia, an ascidian, is con-
structed on the same plan as in the Annulata, but the mode of origin and apparently
dorsal position of the nervous system of the tailed larval ascidian presents features
which apparently anticipate the state of things existing among tlie lower vertebrates,
such as the lancelet.

We need not here describe the different forms of nervous system in the classes of
invertebrates, but refer the reader to the figures and descriptions of the different
types in the body of this work. It will be well to read the following data concerning
the brain and nervous system, which we quote from Bastian's " The Brain as an Organ
of Mind."

"1. Sedentary animals, though they may possess a nervous system, are often head-
less, and they then have no distinct morphological section of this system answering
to what is known as a brain.

" 2. When a brain exists, it is invariably a double organ. Its two halves may be
separated from one another, though at other times they are fused into what appears
to be a single mass.

" 3. The component or elementary pa.'ts of the brain in these lower animals are
ganglia in connection with nerves proceeding from special imjjressible parts or sense-
organs ; r..id it is through the intervention of these united sensory ganglia that the
animal's actions are brought into harmony with its environment or medium.

"4. That the sensory ganglia, which in the aggregate constitute the brain of
invertebrate animals, are connected with one another on the same side, and also with
their fellows on the opposite sides of the body. They are related to one another
either by what appears to be continuous growth, or by means of ' commissures.'

" 5. The size of the brain as a whole, or of its several parts, is therefore alwa3's
fairly proportionate to the development of the animal's special sense-organs. The
more any one of these imjiressible surfaces or organs becomes elal)orated and attuned
to take part in discriminating between varied external impressions, the greater will be
the pi'oportionate size of the ganglionic mass concerned.

"6. Of the several sense-organs and sensory ganglia whose activity lies at the root
of the instinctive and intelligent life (such as it is) of invertebrate animals, some are
much more important than others. Two of them especially are notable for their
greater proportion.al development, viz. : those concerned with touch and vision. The
organs of the former sense are, however, soon outstripped in importance by the latter.

INTRODUCTION. xxvii

The visual sense, and its related nerve-ganglia, attain an altogether exceptional devel-
opment in the higher insects and in the highest molluscs.

" 7. The sense of taste and that of smell seem, as a rule, to be developed to a much
lower extent. In the great majority of invertebrate animals it is even difficult to
point to distinct organs or impressible surfaces as certainly devoted to the reception of
either of such impressions. Nevertheless there is reason to believe that in some
insects the sense of smell is marvellously keen, and so much called into play as to
make it for such creatures quite the dominant sense endowment. It is pretty acute also
in some Crustacea.

" 8. The sense of hearing seems to be developed to a very slight extent. Organs
supposed to represent it have been discovered, principally in molluscs and in a few
insects. It is, however, of no small interest to find that where these organs exist the
nerves issuing from them are most frequently not in direct relation with the brain, but
immediately connected with one of the principal motor nerve-centres .of the body.
It is conjectured that these so-called 'auditory saccules' may, in reality, have more to
do with what Cyon terms the sense of space than with that of hearing. The nature
of the organs met with supports this view, and their close relations with the motor
ganglia also become a trifle more explicable in accordance with such a notion.

" 9. Thus the associated ganglia representing the double brain are, in animals pos-
sessing a head, the centres in which all impressions from sense-organs, save those last
referred to, are directly received, and whence they are reflected on to different groups
of muscles — the reflection occurring not at once, but after the stimulus has passed
through certain 'motor' ganglia. It may be easily understood, therefore, that in all
invertebrate animals perfection of sense-organs, size of brain, and power of executing
manifold muscular movements, are variables intimately related to one another.

"10. But a fairly parallel correlation also becomes established between these
various developments and that of the internal organs. An increasing visceral com-
plexity is gradually attained ; and this carries with it the necessity for a further devel-
opment of nervous communications. The several internal organs with their v.arying
states are gradually brought into more perfect relation with the ))rineipal neiwe-cen-
tres as well as with one another.

"11. These relations are brought about by important visceral nerves in Vermes
and arthropods — those of the ' stomato-gastric systems' — conveying their impres-
sions either direct to the posterior part of the brain or to its peduncles. They thus
constitute internal impressions which impinge upon the Ijrain side by side with those
coming through external sense-organs.

" 12. This visceral system of nerves in invertebrate animals has, when compared
with the rest of the nervous systetn, a greater proportional de\elopment than among
vertebrate animals. Its importance among the former is not dwarfed, in fact, by that
enormous development of the brain and spinal coi'd which gradually declares itself in
the latter.

" 13. Thus impressions emanating from the viscera and stimulating the organism
to movements of various kinds, whether in pursuit of food or of a mate, would seem
to have a proportionally greater importance as constituting part of the ordinary mental
life of invertebrate animals. The combination of such impressions with the sense-
guided movements by which they are followed, in complex groups, will be found to
afford a basis for the development of many of the instinctive acts which animals so
frequently display." .

xxviii THE ANIMAL KINGDOM.

When we rise to the vertebrates we meet with a form of nervous system quite
different from that of any adult invertebrate animal. In all the vertebrates which
have a definite skull — and this only excludes the lancelet and the ascidians — the
brain is a series of close-set ganglia, forming a mass situated in the skull, with definite
relations to the sense-organs, and the spinal cord is situated above the vertebral col-
umn, passing through the spinal canal, which is formcil by the contiguous posterior
arches of the several vertebraj composing tlie sjiinal, or vertebral column.

While the nervous system of all skulled vertebrates has a definite persistent situa-
tion, and with a similar cellular structure, there is a great difference between the brain
of the fishes and that of mammals, including man. In the fishes tlie brain cavity is
small compared with the size of the head, the brain being small, and there is a marked
equality in the size of the different lobes forming the brain, the optic lobes being
larger than the cerebral. In amphibians, such as the frog and toad, the brain is
more like that of fishes than of reptiles, but the optic lobes are a little smaller than
the cerebral, while the cerebellum is smaller than in many fishes. In the reptiles, as
seen in snakes, turtles, and crocodiles, the cerebral lobes begin to enlarge, and exceed
in size the optic lobes. Here the ventricle or cavity of the cerebral lobes is larger
than in the fishes, and the rounded eminence projecting from its anterior and inner
surface, called the ' corpus striatum,' is present for the first time.

In Vjirds the brain cavity is much larger than in any of the foregoing classes of
vertebrates, and the cerebral hemispheres are now greatly increased in size, so as to
partly cover the optic lobes. The cerebellum is also much larger than before, and
it is transversely creased.

Passing from the l)irds to mammals, there is seen to be a great advance in the form
of the brain of the latter animals. The brain cavity is much larger, and this is for the
most part occupied by two portions, the cerebrum and the cerebellum. The cerebral
hemispheres entirely conceal from above the olfactory and optic lobes, the surface is
convoluted, while behind it either touches or overlaps, so as in man to completely
conceal the cerebellum. The cerebral hemispheres, then, form the back of the mam-
malian brain, and the higher orders are usually characterized by an increase both in
the size of the cerebral hemispheres, and as a rule, tliough there are exceptions noted
farther on, in the number and complexity of the convolutions of the surface. Thus in
the highest mammals, especially the gorilla and man, the increased size of the brain
in proportion to the greater bulk of the body is very marked.

Leuret has approximately siiown the average ]iroportional weight of the brain to
the body, in four classes of vertebrates, as follows: in Fishes, as 1 to 5,668; in rep-
tiles, as 1 to 1,321 ; in birds, as 1 to 212 ; in Mammalia, as 1 to 186. The brain is,
however, subject to the same laws as other parts of the body. There is in no organ a
regular and continuous progressive increase in size and complexity in any class of the
animal kingdom. The size of the cerebral hemisphere differs in different monkeys, and,
as has been remarked by Bastian, in the higher tyjies of lower orders the brain is often
better developed than among the lower tyi>es of higher orders. Thus in the Midas
marmoset the convolutions are absent, so that in this respect this jirimate is on a level
with the monotremes and lower marsupials and rodents. In dwarf or small-sized
members of a group the brain is larger in j)roportion to the body than in the full-sized
members. Thus among marsupials, as Owen states, the size of the brain of tiie jiigmy
petaurist is to the size of the body as 1 to 25, while in the great kangaroo it is as 1 to
800; among rodents it is as 1 to 20 in the harvest mouse, but is as 1 to 300 in the

INTRODUCTION. xxix

capybara ; among the Insectivoni it is as 1 to 60 in the little two-toed ant-eater, but
is as' 1 to 500 in the great ant-eater. The brain of a porpoise four feet long may
weigh 1 lb. avoirdupois ; that of a whale {Balcenopterd) 100 feet in length dogs not
exceed 4 lbs. avoirdupois; in Quadrumana the brain of the Midas marmoset is to the
body as 1 to 20 ; in the gorilla it is as 1 to '200.

" But such ratios do not show the grade of cerebral organization in the mammalian
class; that in the kangaroo is higher than that in the bird, though the brain of a
sparrow be much larger in proportional size to the body : and the kangaroo's brain is
superior in superficial folding and extent of gray cerebral surface to that of the
petaurist. The brain of the elephant bears a less proportion to the body than that of
opossums, mice, and proboscidian shrews, but it is more complex in structure, more
convolute in surface, and with ]iro))ortions of i)ros- to mes-encephalon much more
nearly than in the human brain. The like remark ai^plies to all the other instances
above cited." Owen explains these facts by saying that the brain grows more rapidly
than the body, and is larger in projiortion thereto at birth than at full growth ; " so
in the degree in which a species retains the immature character of dwarfishness, the
brain is relatively larger to the body."

The bearing of the facts known as to the relative size of the brain and the convolu-
tions are thus discussed by Bastian : " There cannot therefore be, among animals of
the same order, any simple or definite relation between the degree of the intelligence
of the creature and the number or disposition of its cerebral convolutions — since this
structural feature of the brain seems to be most powerfully regulated by the mere bulk
of the creature to which it belongs." It fails still more, when comparing representa-
tives of different orders. For example, the beaver's brain is almost smooth, while that
of the sheep has numerous convolutions, which both in number and cora]ilexity decid-
edly surpass even those of the dog. Yet among closely related animals and those of
about the same size, especially in species of the same genus, or, as in the case of man,
in individuals of the same species, we may look for some proportional relations between
the development of their cerebral convolutions and their intelligence.

" Size of brain, and with it convolutional complexity, must," Bastian remarks, " be
closely related to the number and variety of an animal's sensorial impressions, and also
to its power of moving continually or with great energy.

"The importance of taking into account the powers of movement possessed
by the animal is fully borne out by the fact that the brain attains such a remarkable
size in the shark, as well as in the porpoise and the dolphin — all of them creatures
whose movements are exceptionally rapid, continuous, and varied. The great increase
in the size of the cerebellum in each of these creatures is, therefore, not so surprising;
but it seems very puzzling, at first sight, to understand why this should be accompanied
by a co-ordinate increase in the development of the cerebral hemispheres. For this,
however, there are two causes, the one general and the other more special. It is a fact
generally observed, that sensorial activity, and therefore intelligent discrimination, in-
creases with an animal's powers of movement ; and secondly, there must be sjiecial
parts of the cerebral hemispheres devoted to the mere sensory appreciation of move-
ments executed. The nerve elements lying at the basis of this latter appreciation,
however they may be distributed through the hemispheres, would naturally be the
more developed (and, consequently, all the more calculated to help to swell the size of
the cerebrum), in proportion to the variety and continuance of the movements which
the animal is accustomed to execute."

XXX . THE ANIMAL KINGDOM.

The tactile sense, or sense of touch is common to all animals ; this is the most fun-
damental sense, of which the other senses are without doubt differentiations. In the
lower Protozoa, such as the Amoeba, the sense of touch which they appear to possess
may be due to the inherent irritability and contractilitj' of the protoplasm of which
their bodies are formed.

In the Infusoria, without doubt, the cilia and the flagella with which these animals
are provided are not only organs of locomotion but also of touch. It is probable that
none of the many-celled animals are without the sense of touch unless some of the
sponges, and the root-barnacles (Sacculina) may be, by reason of their lack of a nervous
system and otherwise degenerate structure, destitute of any sense whatever.

The most important of the sense organs are undoubtedly eyes, as they are the
most commonly met with. The transparent spot in the front of the body of
Eugletia viridis, a protophyte, may possibly be the simplest of all sense organs ; if so,
it anticipates the eye of animals. The simplest forms of eyes are perhaps those of the
sea-anemone, in which there are, besides pigment cells forming a colored mass, refrac-
tive bodies which may break up the rays of light impinging on the pigment spot, so
that these creatures may be able to distinguish light from darkness. The ne.xt step in
advance is where a pigment mass covers a series of refractive cells called crystalline
rods or crystalline cones, which are situated at the end of a nerve proceeding from the
brain. Such simple eyes as these, often called eye-spots, may be observed in the flat
worms, and they form the temjiorary eyes of many larval worms, echinoderms, and mol-
luscs. In some nemertean worms, such as certain species of Police and Neniertes, true
eyes appear, but in the ringed worm, Neophanta celox, Greef describes a remarkably
perfect eye, consisting of a projecting spherical lens, covered by the skin, behind which
is a vitreous body, a layer of pigment separating a layer of rods from the external part
of the retina, outside of which is the expansion of the optic nerve. Eyes are also sit^
uated on the end of the body in some worms, and in a worm called Polyophthalmus,
each segment of the body bears a pair of eyes.

The eyes of molluscs are, as a rule, highly organized, until in the cuttle-fish the
eyes become nearly as highly developed as in fishes, but still the eye of the cuttle-fish
is not homologous with that of vertebrates, since in the former the crystalline rods are
turned towards the opening of the eye, while in vertebrates they are turned away from
the opening of the eye, so that, as Huxley as well as Gegenbaur show, the homology
between the eye of the cephalopods and of the vertebrates is not exact.

While, as we have seen, the eyes of the worms and the molluscs are situated arbi-
trarily, by no means invariably placed in the head, in the crustaceans the eyes assume
in general a definite position in the head, except in a schizopod crustacean {Eiiphmcsia),
where there are eye-like organs on the thorax and abdomen. In insects there are both
simple and compound eyes occupying definitely the upper and front part of the head.

The eyes of the lancelet are not homologous with those of the higher vertebrates,
being only minute pigment spots comparable with those of the worms. In the skulled
vertebrates the eyes are of a definite number, and in all the types occupy a definite
position in the head.

The simplest kind of auditory organ is to be found in jelly-fishes, where an organ
of hearing first occurs. In these animals, situated on the edge of the disc, are minute
vesicles containing one or more concretionary bodies or crystals. Reasoning by ex-
clusion, these are supposed to represent the ear-vesicles or otocysts of worms and
molluscs; and the concretions or crystals, the otoliths of the same kind of animals.

INTRODUCTION. . xxxi

The otoc}'sts or simjile cars of worms and molluscs arc minute and usually
difficult to find, as is the auditory nerve leading from them to the nerve-centres. In
the clam it is to be looked for in the so-called foot. lu the snails, as also in cuttle-fish,
the auditory vesicles are placed in the head close to the brain. The ears of Crustacea
are sacs, formed by inpushings of the integument and filled with fluid, into which hairs
project, and which contain grains of sand which have worked iu from the outside, or
concretions of lime. These are situated in the shrimps and crabs at the base of the
inner antennte, but in a few other Crustacea, as in Mi/sis, they are placed at the base
of the lobes of the tail. In the insects the ear is a sac covered by a tympianum, with a
ganglionic cell within, leading by a slender nerve-fibre to a nerve-centre, and in these
animals the distribution of ears is very arbitrary. In the locust they are situated at the
base of the abdomen ; in the green grassho]:>pers, or katydids, and the crickets, in the
fore tibife ; and it is probable that, in the butterflies, the antennre are organs of hearing.
The vertebrate ears are two in number, and occupy a distinct permanent position in
the skull, however much modified the middle and outer ear become. — (Packard's
Zoology.)

" Throughout the animal kingdom," says Romanes, " the powers of sight and of hear-
ing stand in direct r.atio to the powers of locomotion ;" on the other hand, in fixed or
parasitic animals, the organs of hearing and sight are among the first to be aborted.

The sense of smell is obscurely indicated by special organs in the invertebrate ani-
mals ; nasal organs, as such, being characteristic of the skulled vertebrates. Whether
organs of smell exist in any worms or not is unknown ; there are certain pits in some
worms which may possibly be adapted for detecting odors. In some insects, at least,
the organs of smell are without doubt well developed ; the antennae of the bin-ying
beetles are large and knob-like, and evidently adapted for the detection of carrion. It
is possible that certain organs situated at the base of the wings of the flies, and on the
caudal appendages of the cockroach and certain flies, are of use in detecting odors.

ANIMAL PSYCHOLOGY.

We have seen that animals have organs of sense, of perception, in many cases
nearly as highly developed as in man, and that in the Mammalia the eyes, ears, organs
of smell and touch differ but slightly from those of our own species ; also that the
brain .and nervous system of the higher mammals closely approximate to those of man.
We know that all animals are endowed with sufficient intelligence to meet the ordinary
exigencies of life, and that some insects, birds, and mammals .are able, on occasion, to
meet extraordinary emergencies in their daily lives. These facts tend to prove that
all animals, from the lowest to the highest, possess, besides sensations, certain faculties
which by general consent naturalists call mental, because they seem to be of a kind,
however different in degree, with the mental manifestations of man. Besides in
many if not most highly organized animals, sensations give rise to emotions, and
in the higher animals, as well as man, the latter give rise to thoughts. The study
of mental phenomena is the science of psychology. The study of the sensations and
instincts, as well as reasoning powers, of animals, is called animal psychology. The
materials for the study of animal psychology are derived from the observations of
the actions of animals ; we do not, so to speak, know what is going on in their minds ;
we draw our conclusions, as to whether an animal thinks or reasons, by studying our
own mental processes. The study of human psychology is a most difficult one: one

xxxii THE ANIMAL KINGDOM.

man cannot read other men's minds; he judges of then- mental processes by, their
actions and his own mental processes. In the same manner we conclude that aiumals
reason by judging of their acts alone. If human psychology is an inexact science,
much moi-e so is comparative psychology, which includes human as well as animal
psychology.

Although the Amoeba performs ofierations which are akin to the instinctive acts
of higher animals, it may in general be said that the nervous system is the organ of
mind ; not the brain alone, in animals which have a brain, but the entire nervous
system. The mental manifestations of animals are not alone physiological, i. e. auto-
matic and reflex, but there are, at least in highly organized animals, such as crabs,
insects, spiders, and vertebrates, processes which are psychological as opposed to
physiological.

The elementary or root principle of mind, as distinguished from purely physio-
logical processes, is the power of making a choice between two alternatives presented
to the animal.

As we have said on another occasion, granted that insects have sensibilities, how
are we to prove that they have an intellect? Simply by observing whether they make
a choice between two acts. " On entering a closet, ants unhesitatingly direct their
stejjs to the sugar-bowl in preference to the flour-barrel ; one sand-wasp prefers beetle-
grubs to caterpillars, to store up as food for her young. In short, insects exercise
discrimination, and this is the simplest of intellectual acts. They try this or that
method of attaining an object. In fact, an insect's life is filled out with a round of
trials and failures."

While no one would doubt that an insect has the power of choice or discrimination,
may this also be said of the lowest organisms, such as the Amoeba? Mr. KoTnanes
believes that it can. "Amoeba is able to distinguish between nutritious and non-
nutritious particles, and in correspondence with this one act of discrimination it is
able to perform one act of adjustment ; it is able to enclose and to digest the nutri-
tious particles, while it rejects the non-nutritious." Some protoplasmic and unicellular
organisms are able also to distinguish between light and darkness, and to adapt their
movements to seek the one and shun the other; Mr. H. J. Carter thinks that the
beginnings of instinct are to be found so low down in the scale as the Rhizopoda.
As quoted by Romanes in his Animal Intelligence : " Even Athealhmi will confine
itself to the water of the watch-glass in which it may be placed when away from saw-
dust and chips of wood among which it has been living; but if the watch-glass be
placed upon the saw-dust, it will very soon make its way over the side of the watch-
glass and get to it." Other facts are cited from Mr. Carter, n]ion which Mr. Romanes
makes the following reflections : —

" With regard to these remarkable observations it can only, I think, be said that,
although certainly very suggestive of something more than mechanical response to
stimulation, they are not sufficiently so to justify us in ascribing to these lowest
members of the zoological scale any rudiment of truly mental action. The subject,
however, is here full of difficulty, and not the least so on account of the Amoeba not
only having no nervous system, but no observable organs of any kind ; so that,
although we may suppose that the adaptive movements described by Jlr. Carter were
non-mental, it still remains wonderful that these movements should be exhibited by
such apparently unorganized creatures, seeing that as to the remoteness of the end
.attahied, no less than the complex refinement of the stimulus to which their adaptive

INTRODUCTION. xxxiii

response was ilue, the movements in question rival the most elaborate of non-mental
adjustments elsewhere performed by the most highly organized of nervous systems."

It will be a matter of interest to trace the dawnings of mental processes in the
lower animals. Having seen that something more than physiological effects are trace-
able in certain acts of the protozoans ; passing over the sponges, which are at best
retrograde organisms, w^e come to the ccelenterates, especially the jelly-fishes. In
none of these creatures have actions involving intelligence been observed ; all their
acts, so far as yet observed, are j)hysiological, i. e. reflex, the result of stimulation
from without.

Of the echinoderms, Romanes says : " Some of the natural movements of these ani-
mals, as also some of their movements under stimulation, are very suggestive of purpose ;
but I have satisfied myself that there is no adequ.'Xte evidence of the animals being able to
profit by individual experience, and therefore, in accordance witli our canon, that
there is no adequate evidence of their exhibiting truly mental phenomena. On the
other hand, the study of reflex action in these organisms is full of interest."

It is possible that the action of the earth-worm, a representative of the annelids,
in drawing leaves down into its hole is " strongly indicative of instinctive action, if
not of intelligent purpose — seeing that they always lay hold of the part of the leaf
(even though an exotic one) by the traction of which the leaf will offer least resistance
to being dr.awn down." To the foregoing statement of Romanes we may add Darwin's
testimony as to the mental powers of the earth-worm, from his work entitled The
Formation of Vegetable Mould through the Action of Worms.

" Worms are jioorly provided with sense-organs, for they cannot be said to see,
although they can just distinguish between light and darkness; they are completely
deaf, and have only a feeble power of smell ; the sense of touch alone is well developed.
They can, therefore, learn little about the outside world, and it is surprising that they
should exhibit some skill in lining their burrows with their castings and with leaves,
and, in the case of some species, in piling up their castings into tower-like constructions.
But it is far more surprising that they should apparently exhibit some degree of intel-
ligence instead of a mere blind instinctive impulse, in their manner of plugging up the
mouths of their burrows. They act in nearly the same manner as would a man, who
had to close a cylindrical tube with different kinds of leaves, petioles, triangles of paper,
etc., for they commonly seize such objects by their pointed ends. But with thin ob-
jects a certain number are drawn in by their broader ends. They do not act in the
same unvarying maimer in all cases, as do most of the lower animals ; for instance, they
do not drag in leaves by their foot-stalks, unless the basal part of the blade is as nar-
row as the apex, or narrower than it."

The next gre.it type of animals is the molluscs. In many respects the higher
worms, especially the annelids, are more highly organized than the clam, a snail, or
cuttle-fish. The functions of sensation and locomotion are often in molluscs subordi-
nate to the merely vegetative, such as feeding, nutrition, and reproduction. We
should not, as Rom.anes has said, expect that molluscs would present any considerable
degree of intelligence. " Nevertheless, in the only division of the group which has
sense organs and powers of locomotion highly developed — viz., the Cephalopoda — we
meet with large cejihalic ganglia, and, it would appear, with no small development of
intelligence."

Beginning with one of the lowest molluscs, the oyster, Romanes quotes from Mr.
Darwin's MS, as follows : " Even the headless oyster seems to profit from experience,

xxxiv THE ANIMAL KINGDOM.

for Dicquemase asserts that oysters taken from a depth never uncovered by the sea,
open their shells, lose the water within, and perish ; but oysters taken from the same
place and dujith, if kept in reservoirs, where they are occasionally left uncovered for a
short time, and are otherwise incommoded, learu to keep their shells shut, and they
live for a much longer time when taken out of the water." Is this act simply reflex ?
Limpets have been known, after making excursions from their resting places in order
to browse on seaweed, to return repeatedly to one spot or home. The precise memory
of direction and locality implied by this fact, adds Romanes, "seems to justify us in
regarding these actions of the animal as of a nature unquestionably intelligent."

Concerning snails Darwin remarks : " These animals apjiear also susceptible of some
degree of permanent attachment ; an accurate observer, Mr. Lonsdale, informs me that
he placed a pair of land-shells {ITelix ^lomatia), one of which was weakly, in a small
and ill-provided garden. After a short time the strong and healthy individual disap-
peared, and was traced by its track of slime over a wall into an adjoining well-stocked
garden. Mr. Lonsdale concluded that it had deserted its sickly mate ; but after an ab-
sence of twenty-four hours it returned, and apparently communicated the result of its
successful exploration, for both then started along the same track and disaj^peared
over the wall."

Mr. W. H. Dall gives a remarkable instance of intelligence in a snail, kept as a pet
by a child, which recognized her voice and distinguished it from that of others. The
lady who told the story to the person who sent it to Mr. Dall, after stating that her
sister Geoi'gie was, from the age of three years, quite an invalid, and remarkable for her
j)Ower of putting herself en rapport with all living things, said: "Before she could say
more than a few words, she had formed an acquaintance with a toad, which used to
come from behind the log where it lived, and sit winking before her in answer to her call,
and waddlo back when she grew tired and told it to go away. When slie was between five
and six years of age, I found a snail shell, as I thought, which I gave to her to amuse
her, on my return from a picnic. The snail soon crawled out, to her delight, and after
night disappeared, causing great lamentation. A large, old fashioned sofa in the front
hall was moved in a day or two, and in it was found the snail glued fast ; it had crawled
down stairs. I took a plant jar of violets and, jjlacing the snail in it, carried it to her,
and sunk a small toy cup even with the soil, filling it with meal. This was because I
had read that French people feed snails on meal. The creature soon found it, and we
observed it with interest for a while, as we found it had a mouth which looked pink in-
side and appeared to us to have tiny teeth also. We grew tired of it, but Georgie's
interest never flagged, and she surprised me one day by telling us that her snail knew
her and would come to her when she talked to it, but would withdraw into its shell if
anyone else spoke. This was really so, 'as I saw her prove to one and another time
after time." Mr. Dall adds : " An observer who noticed and remembered the pink
buccal mass, the lingual teeth, and the translucent mistletoe-berry-like eggs, and after
such an interval of time could so accurately describe them, is entitled to the fullest
credence in other details of the story, and I have no doubt of its substantial accuracy,
in spite of its surprising nature."

The Crustacea are perhaps, as regards intelligence, on a level with the majorit)' of
insects, excepting the white ants and ichneumons, wasps, and bees.

The power of finding their way home, which of course is due to memory, is illus-
trated in the following instance published by Mr. E. W. Cox in " Nature " for Ajn-il
3, 1873. "The fishermen of Falmouth catch their crabs off the Liz.ard rocks, and they

INTRODUCTION. XXXV

are brought into the harbor at Falmouth alive and impounded iu a box for sale, and
the shells are branded with marks by which every man knows his own fish. The
place where the box is sunk is four miles from the entrance to the harbor, and that is
above seven miles from the place where they are caught. One of these boxes was
broken ; the branded crabs escaped, and two or three days afterwards they were
again caught by the fisherman at the Lizard rocks. They had been carried to Fal-
mouth in a boat. To regam their home they. had first to find their way to the mouth
of the harbor, and when there, how did they know whether to steer to the right or to
the left, and to travel seven miles to their native rocks?" It is scarcely possible to
regard such an instance of what has been called the ' homing instinct,' as a purely
physiological, reflex act, nor to consider the crab a mere automaton.

Mr. Darwin, in his Descent of Man, refers to the curious instinctive habits of the
large shore-crab {Birc/us latro), which feeds on fallen cocoa-nuts, " by tearing off the
husks fibre by fibre ; and it always begins at that end where the three eye-like depres-
sions are situated. It then breaks through one of these eyes by hammering with its
heavy front pincers, and, turning round, extracts the albuminous core with its narrow
posterior pincers."

Little is really known of the instincts and other intellectual traits of the crusta-
ceans— but when we come to the insects the literature is very extensive, thanks to the
observations of Reaumur, Bonnet, De Geer, Wyman, Bates, Belt, Milller, Moggridge,
Lincecum, McCook, Sir John Lubbock, and others.

As we have stated in our Half Hours with Insects : " Those who observe the ways
of insects have noticed their extreme sensitiveness to external impressions ; that their
motions are ordinarily rapid and nervous. Look at the ichneumon fly as it alights on
a leaf near a caterpillar : with what rapid motions it walks and flies about ; how swiftly
its feelers vibrate ; how briskly it walks uji and down surveying its victim. Look at a
mud wasp as it alights near a pool of water to moisten its mouth. How nervous are
its motions, how nimbly it flies and runs about the edge of the water. The ant is a
busy, active, dapper little creature, a nervous brusqueness pervading its movements.
How susce23tible insects are to the light may be tested on a damji, dark night by open-
ing the windows. In dart a legion of insects of all sorts, each with a different mode
of entrance, some beetle boldly flying about the room in its blundering noisy flight, or
a Clisiocampa moth enters with a bound, and a series of somersaults over the table,
like the entree of a popular clown into the ring of a circus, though the latter may have
the most self-possession of the two.

" Insects are, like most animals, extremely sensitive to electrical phenomena. Just
before a thunder shower they are particularly restless, flying about in great numbers
and without any apparent object. The appendages of insects, their feelers and their
legs, must be provided with exquisitely sensitive organs to enable them to receive im-
pressions from without. Everybody knows that insects have acute powers of sight.
That they also hear acutely is a matter of frequent observation. Often in walking
through dry bushes, the noise of one's feet, in crushing through the undergrowth, starts
up hosts of moths, disturbed in their noonday repose. If insects did not hear acutely,
why should the Cicada have such a shrill cry ? For whose ears is the song of the cricket
designed unless for those of some other cricket ? All the songs, the cries, and hum of in-
sect life have their purpose in nature and are useless itnless they warn off or attract
some other insect.

" We know with a good degree of certainty that some insects have an acute sense

xxxvi THE ANIMAL KINGDOM.

of smell. The carrion beetles scent their booty afar off ; the ants, the moths, all the
insects attracted to flowers by the smell of the honey in them, evidently have well de-
veloped organs of smell."

The internal structure of the brain of the ant, the bee, as well as the locust and other
insects has been found to be unexpectedly complex, when compared with that of the
higher worms and even the higher Crustacea, such as the lobster and cray fish. The
brain of insects is a much more complicated organ than any of the succeeding ganglia,
consisting more exclusively of sensory cells and nervous threads than any succeeding
ones, though the subcesophageal one is also complex, consisting of sensory as well as
motor ganglia, since this ganglion sends off nerves of special sense to the organs of
taste and smell situated in the mouth-appendages. The third thoracic ganglion is also,
without doubt, a complex one, as, in the locusts, the auditory nerves f>ass from it to the
ears, which are situated at the base of the abdomen. But in the green grasshoppers,
such as the katydids and their allies, whose ears are situated in their fore legs, the first
thoracic ganglion is a complex one. In the cockroach and in Leptis ( Ch7ysopila), a
common fly, the caudal appendages bear what are probably olfactory organs, and as
these parts are undoubtedly supplied from the last abdominal ganglion, this is proba-
bly composed of sensory and motor ganglion-cells ; so that we have in the ganglionated
cord of insects a series of brains, as it were, running from head to tail, and thus in a
still stronger sense than in Vertebrates the entire nervous system, and not the brain
alone, is the organ of the mind of the insect.

To briefly describe the brain of the locust, an insect not high in the scale, it is a
double ganglion, but structurally entirely different from, and far more complicated than,
the other ganglia of the nervous system. The cerebral lobes possess a ' central body,'
and in each hemisphere is a ' mushroom body ; ' besides the main cerebral lobes, the
brain has also a pair of optic lobes and optic ganglia, and olfactory or antennal lobes,
and these lobes have their connecting and commissural nerve-fibres, not found in the
other ganglia.

The locust's brain appears to be as highly developed as that of the majority of in-
sects, but that of the ant .and the bee is more complicated than in other winged insects,
owing to the much greater complexity of the folds of the calices or disk-like bodies
ca]>ping the double stalk of the mushroom body. Now the ants, wasps, and bees
are pre-eminently social animals, and we see by the structure of the brain why, in
point of intelligence, they may exceed in mental development even the fishes, rep-
tiles, and other lower vertebrates, and almost rival the birds in instinctive and
rational acts.

Experiments and anecdotes bearing upon the intelligence of ants, have been
widely circulated in the works of Lincecum, MeCook, Lubbock, Darwin, and Romanes,
space not allowing us to reproduce them. Ants have the sense of sight and of
scent and taste well developed, but the sense of hearing is feeble, sounds of various
kinds not producing any effect upon them : their antennte are not, then, as in some
insects, organs of hearing or smell, but have a delicate sense of touch, and, indeed,
are the most important of sense organs to them. The sense of direction, the power
of memory, are highly developed, and they perhaps are not destitute of the tenderer
emotions, individuals being known to display sym])athy for their wounded compan-
ions or healthy friends in distress. Ants also have the power of communicating with
one another, and they are susceptible of education. The young ant is led about the
nest and " trained to a knowledge of domestic duties, especially in the care of the

INTRODUCTION. xxxvii

larvae ; they are also taught to distinguish between friends and foes." When an ant's
nest is attacked by foreign ants, the young ones never join in the fight, but confine
themselves to removing the pupie ; and Forel has by experiment proved that the
knowledge of hereditary enemies is not wholly instinctive in ants.

Moreover, besides carrying on the complicated duties of the formicary, ants add
to their labors by keeping in their nests milch cows, as the Aphides substantially are ;
they also carry on slave-catching wars, and keep slaves generation after generation,
with the same results of enfeebling and deteriorating the body and mind of the mas-
ters, as has been experienced in human life. Ants also keep pets, and, to go to another
extreme, carry on wars of conquest, rapine, and plunder. A few human races are said
not to bury their dead : if this be so they are inferior to ants, whose care in disposing
of the bodies of their dead has attracted the notice of Sir John Lubbock ; and that
they actually in some cases bury their dead was claimed by Pliny, and substantiated
by recent observers, according to Romanes. And then we have the leaf-cutting ants,
harvesting ants, honey-making ants, military ants, ants which bridge streams, dig wells,
and tunnel under broad rivers.

Wasps and bees can see much better than ants; indeed, they ai'e far more depen-
dent than the latter on the power of perceiving flowers, they also have a highly
developed sense of direction, powers of communication, while the combined instinc-
tive and reasoning powers they exhibit in making their nests, and in pi-oviding for or
caring for their young are proverbial. Whether the instinct of building hexagonal
cells is purely automatic or not has been disputed, but now it is conceded by Darwin,
Romanes, and others that the process is not a purely mechanical one, but is " constantly
under the control of intelligent purpose ; " in other words, the worker bee knows what
it is about, is a conscious agent.

Spiders also, though their nervous system is much less complicated than that of
ants and bees, as well as insects in general, being built upon a different plan,
show the most astonishing intellectual powers, particularly in spinning their webs ;
wliile as examples of special instincts the result of reasoning processes, at least in the
beginning, are the acts of the water spiders, and especially the trap-door spiders.

Spiders also, like ants and bees, are able to distinguish between persons, approach-
ing those they know to be friendly, and shunning strangers. It is well known that
spiders can be tamed, and there are well-authenticated anecdotes testifying to the
high degree of intelligence of these creatures.

Passing now to the branch of vertebrates, we do not find a sudden rise in the
intellectual scale from bees to fishes, but that in reality fishes and reptiles are not so
highly endowed mentally as the most highly organized insects. As Romanes truly
says : " Neither in its instincts nor in general intelligence can any fish be compared
with an ant or bee, — a fact which shows how slightly a psychological classification of
animals depends upon zoological affinity, or even morphological organization."
Fishes, he states, " display emotions of fear, pugnacity ; social, sexual, and parental
feelings; anger, jealousy, play, and curiosity. So far, the class of emotions is the
same as that with which we have met in ants, and corresponds with that which is dis-
tinctive of the psychology of a child about four months ol<l."

Of batrachians, frogs and toads have more or less definite ideas of locality, while
they will learn to recognize the human voice and come when called. The general
intelligence of reptiles is higher than that of fishes and batrachians, but low compared
with that of birds. Snakes and tortoises are said to be able to distinguish persons ;

xxxviii THE ANIMAL KINGDOM.

and snakes, when tamed, exhibit some degree of affection for their master or mistress ;
while cobras may not only be tamed but domesticated.

Between the lower vertebrates and the birds and mammals there is a wide intellec-
tual gulf. In birds, the reasoning as opposed to the simply instinctive acts are
jiumerous. Birds are active, volatile, hot-blooded creatures, all their senses acute,
and their cerebral hemispheres are far better developed than in the lower classes.

To illustrate the high degree of intelligence of birds, we will state some of the con-
clusions given by Romanes, referring the reader to his interesting work on Animal
Intelligence for the anecdotes supporting his generalizations. The memory of birds
for localities is well illustrated by their migratory habit of returning year after year
to the same breeding-place. Buekland gives an account of a pigeon which remem-
bered the voice of its mistress after an absence of eighteen mouths. Wilson relates
an instance where a tame crow, after an absence of about eleven months, recog-
nized his master. Parrots, which are perhaps the most intelligent of birds, sometimes
chatter their phrases in their dreams, and " this shows a striking similarity of psychi-
cal processes in the opei-ations of memory with those which occur in ourselves."
Parrots have the jjower of association of ideas, and they not only remember, but
recollect ; " that is to say, they know when there is a missing link in a train of asso-
ciation, and purposely endeavor to pick it up."

Among the emotions, birds for the first time show unmistakable feelings of affec-
tion and sympathy. The loves of birds, the pining for an absent mate, and the con-
jugal affection of doves, etc., proves that in them the sinijile sexual feelings are
heightened and enhanced by the intellect. Their jealousy is proverbial, as seen in
the singing birds ; they also show emulation and resentment as well as vindictiveness ;
their curiosity — the signs of a quick intellect — is highly developed ; they have
aesthetic emotions, love of bright-colored objects shown by the bower-bird, which
builds its bowers at sporting-places in which the sexes meet, and where the males
display their finery. Moreover, the singing birds, which stand at the head of the
avian series, show a decided fondness for the music of their mates, aside from any
utilitarian or sexual motives. Canaries, parrots, and doves are well known to take
delight in human vocal or instrumental music.

The nesting habits of birds call out our admiration not only for their wonderful
architectural traits, but for the signs they exhibit of a plastic instinct, where reason
teaches them to modify their nests in situation and form to adapt them to new condi-
tions. In Montana and Colorado the wild goose builds in trees ; the cuckoo occa^
sionally lays her eggs on the bare ground, sits on them, and feeds her young; the
falcon, which usually builds on cliffs, has been known to lay its eggs on the ground iu
a marsh ; the house-swallow in the United States has changed its nesting habits since
the country was settled and houses were built. The nests of young birds, as first
noticed by "Wilson, are distinctly inferior to those of older ones, both in situation and
construction. " As we have here independent testimony of two good observers to a
fact which in itself is not improbable, I think we may conclude that the nest-making
instinct admits of being supplemented, at any rate in some birds, by the experience
and intelligence of the individual. M. Pouchet has also recorded that he has found a
decided improvement to have taken place in the nests of the swallows at Rouen
during his own lifetime; and this accords with the anticipation of Leroy, that if our
observations extended over a sufiieient length of time, and in a manner sufiiciently
close, we should find that the accumulation of intelligent improvements by individuals

INTRODUCTION. xxxix

of successive generations would begin to tell upon the inherited instinct, so that all
the nests in a given locality would attain to a higher grade of excellence. Leroy also
states that, when swallows are hatched out too late to migrate with the older birds, the
instinct of migration is not sufficiently imperative to induce them to undertake the
journey by themselves. They perish the victims of their ignorance, and of the tardy
birth which made them unable to follow their parents."

Among the higher mammals are the true domestic animals, the friends of man, who
are capable of education and of transmitting striking hereditary traits. Among the
Educabilia we find the horse, dog, pig, ox, sheep, llama, dog, cat. Romanes insists that
the horse is not so intelligent an animal as any of the larger Carnivora, while among her-
bivorous quadrupeds his sagacity is greatly exceeded by that of the elephant, and in
a lesser degree by that of his congener the ass. We question whethpr any one who
has seen Baitholomew's "Equine Paradox," the twelve trained horses, will not ])lace
their intelligence at least as high as that of the pig. Pigs exhibit a degree of intelli-
gence which "falls short only of that of tlie most intelligent Carnivora." Romanes
claims that the tricks taught the so-called "learned pig" would alone suffice to show
this; "while the marvellous skill with which swine sometimes open latches and fasten-
ings of gates, etc., is only equalled by that of tlie cat."

Among the Carnivora in a wild state, bears claim a high place in the psycholog-
ical scale; the most astonishing anecdote is one published in "Nature" since the
appearance of Mr. Romanes' book. The story relates to a Russian bear. "The
carcass of a cow was laid out in the woods to attract the wolves, and a spring trap
was set. Next morning the forester found there the track of a bear instead of a wolf
on the snow ; the trap was thrown to some distance. Evidently the bear had put his
paw in the trap and had managed to jerk it off. The next night the forester hid
himself within shot of the carcass, to watch for the bear. The bear came, but first
pulled down a stack of firewood cut into seven-foot lengths, selected a piece to his
mind, and, taking it up in his arms, walked on his hind legs to the carcass. He then
beat about in the snow all round the carcass with the log of wood before he began his
meal. The forester put a ball in his head, which I almost regret, as such a sensible
brute deserved to live."

Of the rodents, the majority, as the guinearpig, hare, rabbit, etc., are low in intelli-
gence; the squirrels have however some striking instincts, while the house rat, per-
haps as the result of generations of persecution by man, has shown much intelli-
gence ; but the reasoning powers exhibited by the beaver are not only exceptional
among rodents, but unique among dumb animals. In his admirable book on the
beaver, the late Mr. Lewis H. Morgan thus speaks regarding what he calls the free
intelligence of this animal : " The works of the beaver afford many interesting illus-
trations of his intelligence and reasoning capacity. Felling a tree to get at its
branches involves a series of considerations of a striking character. A beaver seeing
a birch tree full of spreading branches, which to his longing eyes seemed quite
desirable, may be supposed to say within himself: 'If I cut this tree through with
my teeth it will fall, and then I can secure its limbs for my winter subsistence.' But
it is necessary that he should carry his thinking beyond this stage, and ascertain
whether it is sufficiently near to his pond, or to some canal connected therewith, to
enable him to transport the limbs, when cut into lengths, to the vicinity of his lodge.
A failure to cover these contingencies would involve him in a loss of his labor. The
several arts here described have been performed by beavers over and over again.

xl THE ANIMAL KINGDOM.

They involve as well as prove a series of reasoning processes undistinguishable from
similar processes of reasoning ])erformed by the human mind.

"Again, the construction of a canal from the pond, across the lowlands to the I'ising
ground upon which the hard wood is found, to provide a way for the transportation
of this wood by water, is another remarkable act of animal intelligence. A canal is
not absolutely necessary to beavers any more than such a work is to mankind ; but it
comes to both alike as the progress in knowledge. A beaver canal could only be con-
ceived by a lengthy and even complicated process of reasoning. After the concep-
tion had been developed and executed in one place, the selection of a line for a canal
in another would involve several distinct considerations, such as tlie character of the
ground to be excavated, its surface elevation above the level of the pond, and the
supply of hard wood near its necessary terminus. These, together with many other ele-
ments of fitness, must be ascertained to concur before the work could be safely entered
upon. When a comparison of a large number of these beaver canals has demonstrated
that they were skilfully and judiciously located, the inference seems to be unavoidable
that the advantages named were previously ascertained. Tliis would require an
exercise of reason in the ordinary acceptation of the term.

" And this leads to another suggestion. Upon tlic upper Missouri these canals are
impossible from the height of the river-banks ; and besides this they are unnecessary, as
the cotton-wood, which is the prevailing tree, is found at the edge of the river. While,
therefore, canals are unknown to the Missouri beavers, they are constantly in use among
the beavers of Lake Superior. On the other hand, the ' beaver slides ' so common and
so necessary on the upper Missouri are unnecessary, and therefore unknown, in the Lake
Superior region. Contrary to the common opinion, is there not evidence of a progress
in knowledge to be found in the beaver canal and the beaver slide ? There was a time,
undoubtedly, when the canal first came into use, and a time, consequently, when it was
entirely unknown. Its first introduction was an act of progress from a lower to a higher
artificial state of life. The use of the slide tends to show the possession of a free intelli-
gence, by means of which they are enabled to adapt themselves to the circumstances by
which they are surrounded. In like manner it has been seen that the lodge is not
constructed upon an invariably typical plan, but adapted to the jiarticular location in
which it is placed. The lake, the island, and the bank lodge are all different from
each otlier, and the diffei-ence consists in changes of form to meet the exigencies of
the situation. These several artificial works show a capacity in tlie beaver to adapt
his constructions to the particular conditions in which he finds himself placed.
Whether or not they evince progress in knowledge, they at least show that the beaver
follows, in these respects, the suggestions of a free intelligence."

The elephant is not only a most sagacious animal, but displays emotions of a high
grade. Were the elepliant bred in captivity, we might expect a still greater degree of
intelligence, but it should be borne in mind that the individuals used as beasts of
burden are hunted and tamed, arid their intelligence dies with them. Romanes
claims tliat "the higher mental faculties of the elephant are more advanced in their
development than in any other animal, except the dog and monkey."

Then comes the cat, whose intelligence is scarcely overrated by the popular
judgment. Of all the cat stories we have read, the following one, copied from
Romanes, caps the climax for the display of good judgment under trying circum-
stances: while a p.araffine lamp was being trinnned, some of tlie oil fell upon tlie back
of the cat, and was afterwards ignited by a cinder falHng upon it from the fire. " The

INTR OD UC TION. xli

cat, with her back in a blaze, in an instant made for the door (which happened to be
open) and sped up the street about one hundred yards, where she phinged into the vil-
lage watering trough, and extinguished the flame. The trough had eiglit or nine inches
of water in it and puss was in the habit of seeing the fire jnit out with water
every night."

The dog is par excellence the friend of man, and without doubt his mind has been
moulded as no other animal's, by that of his master. " The intelligence of the dog,"
says Romanes, "is of special, and, indeed, of unique interest, from an evolutionary
point of view, in that from time out of record this animal has been domesticated
on account of the high level of its natural intelligence ; and by persistent contact with
man, coupled with training and breeding, its natural intelligence has been greatly
changed. In the result we see, not only a general modification in the way of depend-
ent companionship and docility, so unlike the fierce and self-reliant disposition of all
wild species of the genus ; but also a number of special modifications, peculiar to
certain breeds, which all have obvious reference to the requirements of man." Dogs
have long memoi'ies, and they are superior to all other animals in their highly devel-
oped emotions. They can communicate simple ideas to one another as well as to
their master, through the medium of a canine sign-language.

Reacliing the highest order of mammals, the Primates, we are confronted with
what Romanes may be correct in supposing to be " a mental life of a distinctly differ-
ent type from any that we have hitherto considered, and that in their psychology, as
in their anatomy, these animals approach most nearly to Homo sapiens." This, liow-
ever, is an open question, and it is held by some that other animals, as the dog, exceed
tlie monkeys and apes in intelligence. We are not sure, however, but tliat the monkeys
and apes would, if bred in domestication for successive generations, prove that their
highly developed brains place them on a higher psychological level than the dog, cat,
elephant, hare, or pig. " The orang," says Romanes, " which Cuvier had, used to draw
a chair from one end to the other of a room, in order to stand upon it so as to reach a
latch which it desired to open ; and in this we have a display of rationally adaptive action
which no dog has equalled, although ... it has been closely approached. Again,
Rengger describes a monkey employing a stick wherewith to pry up the lid of a chest,
which was too heavy for the animal to raise otherwise. This use of a lever as a mechan-
ical instrument is an action to which no animal other than a monkey has ever been known
to attain ; and, as we shall subsequently see, niy own observation has fully corroborated
that of Rengger in this respect. More remarkable still, as we shall also subsequently see,
the monkey to which I allude as having myself observed, succeeded also by methodical
investig.ition, and without any assistance, in discovering for himself the mechanical
principle of the screw; and that monkeys well understand how to use stones as
hammers is a matter of common observation since Dampier and Wafer first described
this action as practised by these animals in the breaking open of oyster-shells."

As regards the brains of ajies, Bastian remarks : " In the conformation of their
brain, the chimpanzee, the gorilla, and the orang approach, as we have seen, most
closely to that of man ; but it must never be forgotten that although in general shape,
in the disposition of its fissures, and in the arrangement of its convolutions, as far as
they go, there is this striking resemblance to the human brain, yet in actual size oi-
weight, the brain of the man-like apes is widely separated from that of man. The
heaviest brain belonging to one of these creatures, as yet examined, has been barely
one half of the weight of the smallest normal human brains, although the weight of

xlii THE ANIMAL KINGDOM.

the entire body in the great gorilla may be nearly double that of an ordinary man.
The brains of these three kinds of ' man-like ' apes differ considerably among them-
selves ; as we have seen, each in some respects approaches nearer to that of man than
the others, though on the whole it is considered that the brain of the orang is slightly
higher in type than that of the other two."

Bastian also quotes, as follows, from David Hartley's "Observations on Man"
(1834) : " It is remarkable that apes, whose bodies resemble the human body more
than those of any other brute creature, and whose intellects also a])proaeh nearer to
ours, — which last circumstance may, I suppose, have some connection with the first,
— should likewise resemble us so much in the faculty of imitation. Their aptness in
handling is plainly the result of the shape and make of their fore legs and their intel-
lects together, as in us. Their peculiar chattering may perhaps be some attempt
towards speech, to which they cannot attain, partly from the defect in the organs,
partly, and that chiefly, from the narrowness of their memories, appi-ehensions, and
associations."

We will close this too rapid view of the supposed facts in animal psychology by
quoting from Bastian the following anecdote from Leuret : " One of the orangs, which
recently died at the menagerie of the Musee, was accustomed, when the dinner hour
had come, to open the door of the room where he took his meals in company with
several jsersons. As he was not sufficiently tall to reach as far as the key of the door,
he hung on to a rope, balanced himself, and, after a few oscillations, very quickly
reached the kej-. His keeper, who was rather worried by so much exactitude, one day
took occasion to make three knots in the rope, which, having thus been made too short,
no longer permitted the orang-utan to seize the key. The animal, after an ineffectual
attempt, recorjnizing the nature of the obstacle which ojj^Msed his desire, climbedup the
rope, placed himself above the knots, and untied all three, in tlie presence of M. Geof-
frey Saint-Hilaire, who related the fact to me. The same ape wishing to open a door,
his keeper gave him a bunch of fifteen keys ; the ape tried them, in turn, till he had
found the one which he wanted. Another time a bar of iron was put into his hands,
and he made use of it as a lever."

Let us now look at the inductions which may be drawn from the facts now known
regarding the intelligence of animals. It is evident that animals are not mere ])hysi-
ological machines. We may, with Romanes, reject the view of Descartes, Huxley, and
others, that animals are merely automata, on the ground that it can never be accepted
by common sense, while " by no feat of logic is it possible to make the theory apply to
animals to the exclusion of man."

We discern in the mental traits of animals, besides reflex acts, those which are in-
stinctive and those which are the result of reasoning processes. The following defi-
nitions, by Mr. Romanes, will answer well our purjiose : " Reflex action is non-mental
neuro-muscular adjustment, due to the inherited mechanism of the nervous system,
which is found to respond to particular and often recurring stimuli, by giving rise to
particular movements of an adaptive, though not of an intentional kind.

" Instinct is reflex action into which there is imported the element of conscious-
ness. The term is therefore a generic one, comprising all those faculties of mind
which are concerned in conscious and adaptive action, antecedent to individual expe-
rience, without necessary knowledge of the relation between means employed and ends
attained, but similarly pei-formed under similar and frequently recurring circumstances
by all the individuals of the same species.

INTRODUCTION. xliii

" Reason, or intelligence, is the faculty which is concerned in the intentional adap-
tation of means to ends. It therefore implies the conscious knowledge of the relation
between means employed and ends attained, and may be exercised in adaptation to
circumstances novel alike to the experience of the individual and to that of the
species."

It would appear, then, that animals have, in some slight degree, vk'hat we call mind,
with its threefold divisions of the sensibilities, intellect, and will. When we study anunals
in a state of domestication, especially the dog or horse, we know that they are capable of
some degree of education, and that they transmit the new traits or habits which they
have been taught to their offspring ; so that what in the parents were newly acquired
habits become in the descendants instinctive acts. We are thus led to suppose tliat
the terse definition of instinct, by Murphy, that it is ' the sum of inherited habits,' is
in accordance with observed facts. Indeed, if animals have sufficient intelligence to
meet the extraordinary emergencies of their lives, their daily so-called instinctive acts,
requiring a minimum expenditure of mental energy, may have originated in previous
generations ; and this suggests that the instincts of the present generation may be the
sum total of the inherited mental experiences of former generations.

Descartes believed that animals were automata. Lamarck expressed the ojiinion
that instincts were due to certain inherent inclinations arising from habits impressed
upon the organs of the animals concerned in producing them.

Darwin does not attempt any definition of instinct ; but he suggests that ' several
distinct mental actions are commonly embraced by this term,' and adds that ' a little
dose, as Pierre Huber expresses it, of judgment or reason often comes into play, even
in animals low in the scale of nature.' He indicates the points of resemblance be-
tween instincts and habits, shows that habitual action may become inherited, especially
in animals imder domestication; and since habitual action does sometimes become
inherited, he thinks it follows that " the resemblance between what originally was a
habit and an instinct becomes so close as not to be distinguished." He concludes
that, by natural selection, slight modifications of instinct which are in any way use-
ful accumulate, and thus animals have slowly and gradually, " as small consequences
of one general law," acquired, through successive generations, their power of
acting instinctively, and that they were not suddenly or specially endowed with
instincts.

Rev. J. J. Murphy, in his work entitled Habit and Intelligence, seems to regard
instinct as the sum of inherited habits, remarking that "reason differs from instinct
only in being conscious. Instinct is unconscious reason, and reason is conscious in-
stinct." This seems equivalent to saying that most of the instincts of the present
generation of animals are unconscious automatism, but that in the beginning, in the
ancestoi-s of the present races, instincts were more plastic than now, such traits as
were useful to the organism being preserved and crystallized, as it were, into the
instinctive acts of their lives. This does not exclude the idea that animals, while in
some respects automata, occasionally perform acts which transcend instinct ; that they
are still modified by circumstances, especially those species which in any way come in
contact with man ; are still in a degree free agents, and have unconsciously learned, by
success or failure, to adapt themselves to new surroundings. This view is strength-
ened by the fact that there is a marked degree of individuality among animals. Some
individuals of the same species are much more intelligent than others ; they act as
leaders in different operations. Among dogs, liorses, and other domestic animals,

xliv THE ANIMAL KINGDOM.

those of dull intellect are led or excelled by those of greater intelligence, and this
indicates that they are not simple automata, but are also in a degree, or within their
own sphere, free agents.

REPRODUCTION AND EMBRYOLOGY.

On a previous page, as an iiitrodtiction to the subject of tissues, we discussed some
of the earlier features of the development of animals, but now we need, in a brief
manner, to consider the subject from another jioint of view, and, in a general way, to
trace it out for the whole animal kingdom.

As soon as the microscope was perfected and constantly used by morphologists as
an instrument of exact research, a flood of light was thrown ujjon the subject of repro-
duction. In its ultimate analysis reproduction essentially consists in the separation of
a portion of an adult animal from itself, this portion developing into an animal like the
parent. It was seen that in the one-celled animals this process was identical with cell
division, and it was called fission. It was also found that, as in the Hydra and allied
polyps, a bud would form, and develoj) into a Hydra, and finally separate from the
original parent Hydra. Although in the first place the formation of the bud is due
to cell-division, a single cell giving rise to the bud, this process is called budding or
gemmation. It was likewise discovered that in those animals which produce eggs, the
latter were fertilized by a very minute and greatly modified cell, called the sperm-cell,
or spermatozoon.

Now, in most of the many-celled animals there are two kinds of individuals, one
female, which produces in its ovaries eggs, and the other the male, which produces in
its testes the spermatozoa. Reproduction, or fertilization of the egg, in such animals,
consists in the fusion of the sperm-cell with the nucleus of the egg; this is called sex-
ual reproduction. From the moment of fertilization begins the life of the germ,
which is called an embryo, while the history of the changes undergone by the embryo
from the time of fertilization of the egg to maturity is called Embryology.

As was said a few pages back, the egg is essentiallj' a simple cell, and in its earlier
condition it is not to be distinguished from the other cells of the reproductive organs,
but with development it changes in many respects, prominent among which is an in-
crease in size. The essential part of the egg is its protoplasm, but to this is usually
added a varying quantity of a nutritive material, the deutoplasm or food-yolk. Besides,
in most forms, protective envelopes, etc., are added. The most familiar egg, that of
the barnyard fowl, is poorly adapted to give us an idea of the true nature of an egg.
Here the protoplasm is very small in quantity, and forms but a small patch on one side
of the ' yolk,' which is almost entirely protoplasm. Another adventitious substance is
the ' white,' while the shell and the membranes are merely protective, and not essential
features. In another respect this egg is unsuited for our purposes, for, at the time of
laying, the segmentation has progressed to a considerable extent, and the egg is no
longer to be regarded as a simple cell.

The tyjiical egg, then, is a mass of protoplasm, which is differentiated, as in any
other cell, into nucleus and nucleolus, the latter in turn exhibiting a structure to be de-
scribed below. In almost all eggs there is found cine or more protective envelopes,
which, according to the mode of origin, have received different names. When it is
produced by the egg itself, it is called the vitelline membrane ; when by the ovarian
tissues of the parent it receives the name chorion. These envelopes in many forms

INTRODUCTION. xlv

are perforated by one or more minute openings which serve for the passage into the
egg of nutritive material from the parent, and for the introduction of water in aquatic
forms. Besides, in many forms there is a larger opening, the micropyle, for the entrance
of tlie spermatozoon which is to fertilize the egg.

Recent investigations have shown that an egg or a cell is far from the simple
structure which it was once imagined to be ; tlie protoplasm of the cell is not a homo-
geneous substance, while the nucleus or germinative vesicle is very complex. The latter
is enveloped by a special membrane and filled witii a protoplasm, in which floats a tan-
gled network of fibres. What is called the nucleolus is now regarded by Flemming
and by Carnoy (two of the most profound students of cells) as a sj)ecialized jjortion or
portions of the network. The nucleolus (there may be three or more in an egg) is
called in the older works the germinative spot, or the Wagnerian vesicle, the latter
name being applied in honor of its first discoverer. In the living egg the nucleolus
is usually readily distinguished under the microscope by its great refrangibility, but to
recognize the network it is necessary to employ stains and other reagents.

This egg, as we have described it, undergoes an extensive and complicated series
of changes (known as the maturation of the egg) before it is ready for impregnation,
although it is to be noted that in some instances the maturation is concomitant
with impregnation. These changes may be summarized as follows : — At first the
nucleus occupies a position near (but rarely at) the centre of the egg ; it now moves to
near the surface, where its membrane breaks down, and the filaments, etc., almost en-
tirely disappear or at least lose their former character. In the place where the last
remnants of the nucleus were seen, there now appears a spindle-shaped body made up
of granules arranged in lines, while from either end other
lines of granules are arranged in a radial manner. The
whole presents an appearance closely similar to that seen
when iron filings are exposed to the influence of a horse-
shoe magnet, wliile from its resemblance to two stars joined
it has received the name amphiaster. It may be observed
in passing, that amphiasters are characteristic not only of *'"^giJbuir-^°™i^\'*us-°' ''oi^r
the matui-ation of the egg, but of cell division as well; globule'; s, spindle shaped

°^' _ _ ' bgure.

the connection between the two will apjiear in the sequel.

The maturation spindle usually takes a position at nearly right angles to the surface of
the egg, and soon from the outer end a prominence appears, extending out beyond the
rest of the egg. The spindle now divides, and the prominence separates from the egg
and forms what is known as a polar globule. Again the portion of the spindle which
remains within the egg approaches the surface and a second polar globule is formed in
the same manner as the first. Now, the part of the spindle left in the egg assumes a
nearly spherical condition, and sinks back into the egg, where it appears exactly like
the original nucleus. It is called the female pronucleus.

The meaning of these wonderful jihenomena is far from evident. The best expla-
nation as yet' advanced, is that given by Balfour and Minot independently, which
gains additional plausibility from the fact that essentially similar phenomena arc seen
in the formation of the male re])roductive elements, the spermatozoa. In brief it is
this: — All cells have inherited from their protozoan ancestors the elements of both
sexes ; they are hermaphroditic, and the eggs and spermatozoa cells are the same. Be-
fore they can unite it is necessary that each should get rid of the element to be sup-
plied by the other, and in this light the formation of the polar globules is to be viewed

xlvi

THE ANIMAL KINGDOM.

as an elimination of the male portion from the egg, while, mutatis mutandis, the same

may be said of the remnants of the mother-cells from which the sjjermatozoa are

formed.

Now the egg is ready for that union with the male element, or spermatozoa, which is

called fertilization or impregnation. The process in most if not all forms is essentially

as follows : One or more spermatozoa enter the egg ; in some
cases it has been found that, if more than one entered, the re-
suit was a malformation, to be noticed below ; in other eggs,
on the contrary, several spermatozoa are necessary for fertili-
-/ zation. As soon as the head of the spermatozoon enters the

„ ,.,, ^ ^ egg, it forms a clear space known as the male pronucleus.

Fig. \ II. — Entrance of sperma- =°' . ^ ^

tozoan into egg, and forma- Around this radial striffl apijear, and it slowly travels toward

tion of male pronucleus (m); ., . .

/, female pronucleus; s.sper- the female pronucleus uiitil the two Unite. This compound

matozoau. ,1. t • 1 1 • 1

Structure, tlius formed, is known as the segmentation nucleus.
Now begins the segmentation which was de-
scribed briefly on a 2:)receding page, which results
in the conversion of the egg into a mass of cells,
and which need not be repeated here. One inter-
esting fact, however, may be mentioned. Hermann
Fol, in his studies on the development of the star-
fish, found that, if several spermatozoa obtained
entrance to the egg, a corresponding number of
segmentation nuclei were formed ; and although
development proceeded but a short distance, the
results of this abnormal condition were visible
throughout. Each nucleus formed a centre of seg-
mentation, and when the time arrived for the form-
ation of a gastrula, the same influence was felt, and,
as shown in the adjacent cut, there were several
invaginations. These observations possess a high interest from a teratological point
of view, as they may afford an explanation of the formation of double monsters.

Metamorphosis.
After the formation of the germ layers as described on pages ix. to xii., the develop-
ment of the various organs proceeds, for the details of which one should consult the
accounts of the different groups in the body of this work, and especially Balfour's clas-
sic Treatise on Comi)arative Embryology. Still we may consider here some of the
questions connected with metamorphosis. This term, which has been employed for
many years, is used to indicate the series of changes which an animal undergoes after
being born or after hatching from the egg. In some cases the changes are very slight,
the young leaving the egg in nearly the adult form, while in others, of which a famil-
iar instance is furnished by the butterfly, the modifications which are introduced be-
tween the egg and the mature condition are most startling. As otlier examples of
these complete metamorphoses, we would refer the reader to the jelly-fish, star-fish, sea-
mxhins, worms, molluscs, insects, crustaceans, and l)atrachians, as described in the body
of this work. One of the most curious is that presented by the larval form known as
Actinotrocha, which converts itself into the mature worm T'horonis, by apparently
turning itself inside out. If the reader will compare different accounts; and notice that

Fig. VIII. — Abnormal gastrulation in an
echinodenn, tlie result of multiple im-
pregnation.

INTRODUCTION. xlvii

in the same group, sometimes, as in the case of Halanoglossus, even in the same genus,
one species will develop directly, while another has a complicated life history, he will
be led to the inquiry. What is the meaning, what the use of this metamoqiliosis in
one and not in the other? If one examines carefully the embryological changes of
those forms hatched in the form of the adult, he will see that frequently they present,
while in the egg, an epitome of the development of their relatives in which the changes
have been much more marked. The question is largely one of nutrition, though many
other conditions enter into the problem. In those forms where the food supply in the
egg is abundant, the tendency is to simplify the develoi^iment and to accelerate it. All
superfluous features are consequently omitted, or are passed in a hasty manner. On
the other hand, where the amount of food is small, the animal is forced to begin life
for itself at an early date, and hence it needs every protection against the dangers
of its environment.

An interesting point to be noticed in this connection has recently been described by
Mr. W. J. Sollas, in the development of the sponge, Halisarca. In the Mediterra-
nean the embryos of this sponge escape from the tissues of the parent when they
have arrived at the blastula condition, and they then swim about freely by means of the
cilia clothing the surface ; in the same species on the shores of the English Channel,
the young are retained until after gastrulation and the formation of the canal system.
According to Sollas the exidanation of this difference is not difficult. In the Medi-
terranean there are no strong currents, and it is evidently best for the parents to get
rid of the young at as early a moment as possible, thus escaping a longer drain upon
its energies. In the English Channel, on the other hand, the current is very strong,
and were the embryos to be set free at the stage at which they are in the Mediterra-
nean, the chances are that they would be swept away from proper places for their
further development, and hence they are retained until nearly ready for attachment to
the rocks.

The same influences, nutrition and environment, affect other forms. Almost all
crustaceans undergo a complicated metamorphosis, and in their various stages they
lead very different lives. In the young they are usually free-swimming, and hence
they need protection from aquatic foes. This is usually gained in two ways ; by trans-
parent tissues which render them invisible to fishes, and by the development of spines
and processes from the body, which increases their size without materially adding to
their weight, thus preventing their entrance to the mouths of the smaller forms. Still
not all the Crustacea undergo these changes ; in the whole group of tetradoeapods no
metamorphosis is known, while in the land-crabs of the tropics the young, when
hatched, are closely similar to the parents. In this latter instance, where the adults
live on the land, only going to the sea at the .approach of the breeding season, it is easy
to be seen why the development should be direct.

In other cases the use of larval forms is very evident. Many forms, like the bar-
nacles, s]3onges, and the oysters, lead a stationary life, but the young are free-swim-
ming. This change in form and mode of life undoubtedly is of great benefit to the
species, for if at a given moment the parents were swept out of existence, the young,
living in a different station, would continue the species; and, besides, they serve to
distribute the race from point to point.

The foregoing paragraphs have reference to the larval forms, and the persistence and
value, and the benefits of a metamorphosis. Some of these characters are engrafted on
the primitive stock, wliile others are due to the origin, the evolution of the group, and

xlviii THE ANIMAL KINGDOM.

in all discussions the greatest care must be taken to discriminate between the ancestral
and the adaptive features. We can best illustrate this by taking the case of the de-
velopment of a mammal, and showing how in its various stages it presents a compen-
dium of its history, When, in the mammalian germ, the nervous system and
notochord arise, it is on a level with the larva of an Ascidian ; with the formation of
protovertebrae, it represents the Amphioxus ; a brain, and gill clefts and limbs, indicate
a fish and amphibian stage ; the development of an allantois and closure of the gill
clefts places it on an avian plane ; while with the appearance of a placenta the mam-
malian features are assumed. These successive stages of the individual are closely
paralleled by that of the class. The fleshy, boneless form of Amphioxus and the
tunicates would not be preserved, but from fishes to man the sequence of remains in
the rocks accords with that derived from embryology. It must not be understood
from this that the mammals have been derived from the birds. The true line of descent
is far different, as will be explained on a subsequent page. It merely indicates that
the mammal and the bird have arisen from a common stock, and have pursued the
same course during a jjortion of their history.

Alteknation of Geneeations and Parthenogenesis.

Having spoken of the normal method of development of animals, we may turn to
certain unusual or abnormal modes of production. As an examjjle of what is known
as alternation of generations may be cited the history of the jelly-fish, such as the
naked-eyed medusas {Melicertum and Gampanularin)., which at one time of life
develop by budding, at another by eggs ; of the trematode worms, the adult forms of
which lay eggs, while the redia or proscolex of the same worm produces cercarise by
internal budding. Here also may be cited the cases of strobilation of Aurelia, the
tape-worm, Nais, Syllis, and AiUolytus, among annelids. Thus among coelenterates
and worms, as well as some Crustacea, a large number of individuals are produced,
not from eggs, but by budding.

Similar occurrences take place among insects, as the A2)his or plant-louse, in which
a virgin Aj^his may bring forth in one season nine or ten generations of Ajihides, so
that one A})/iis may become the parent of millions of young. These young directly
develop from eggs or buds which are never fertilized, hence the term parthenogenesis,
or virgin-reproduction, sometimes called agamogenesis (or birth without marriage).
The bark-lice as well as the Apliides develop in this manner during the warm weather;
but at the api)roach of cold both male and female Ai)hides and Coccidse appear, the
females laying fertilized eggs, the first spring brood thus being produced in the nor-
mal, usual manner.

Still more like the production of young in the redia of the trematode worms is the
case of the larva of a small gall-gnat (3Iiastor), which during the colder part of
the year from autumn to spring produces a series of successive generations of larvae
like itself, until in June the last brood develops into sexually mature flies, which lay
fertilized eggs.

While the larval Miastor produces young like itself, the pupa of another fly,
Chironomus, also lays unfertilized eggs from which the flies arise.

A number of moths, inclu<ling the silk-worm moth, are known to lay unfertilized
eggs which produce caterpillars. Among the Hymenoptera, the currant saw-fly, cer-
tain gall-flies, several species of ants, wasps (Polistes), and the honey-bee, are known
to produce fertile young from unfertilized eggs ; in the case of the ants and bees, the

INTRODUCTION. xlix

workers lay eggs which result in the production of males, while the fertilized eggs laid
by the female ant or queen bee produce females or workers.

Taking all these cases together, parthenogenesis is seen to be due to budding, or
cell-division or multiplication. Now it will be remembered that the egg develops
into an animal by cell-division, so that fundamentally parthenogenesis is due to cell-
division, the fundamental mode of growth ; hence, normal growth and partheno-
genesis are but extremes of a single series. In this connection, it will be remembered
that all the Protozoa reproduce by simple cell-division, that among them the sexes are
differentiated, that they do not reproduce by fertilized eggs ; hence, so to speak, among
Protozoa, parthenogenesis is the normal mode of reproduction ; and when it exists in
higher animals it may possibly be a survival of the usual protozoan means of stocking
the world with unicellular organisms, with which we know the waters teem. And
this leads us to the teleology or explanation of the cause why parthenogenesis has sur-
vived here and there in the world of lower organizations ; it is plainly, when we look
at the millions of Aphides, of bark-lice, the hundreds of thousands inmates of ant-
hills and bee-hives, for the purpose of bringing immediately into existence great
numbers of individuals, thus ensuring the success in life of certain species exposed to
great vicissitudes in the struggle for existence. That this unusual mode of reproduc-
tion is all-important for the maintenance of the existence of most of the parasitic
worms, is abundantly proved when we consider the strange events which make up the
sum total of a fluke or tape-worm's biography. Without this faculty of the compara-
tively sudden production of large numbers of young by other than the slow, limited
process of ovulation, the species would be stricken ofE the roll of animal life.

Dimorphism and Poltmokphism.

Involving the production of young among many-celled animals (Metazoa) by what
is fundamentally a budding process, we have two sorts of individuals. When the
organism is high or specialized enough to lay eggs which must be fertilized, we have a
differentiation of the animal into two sexes, male and female. Reproduction by bud-
ding involves the differentiation of the animal form into three kinds of individuals — •
i. e., males, females, and asexual individuals, among insects often called workers or
neuters. These have usually, as in ants and bees, a distinct form, so as to be
readily recognized at first sight. Among the Ccelenterata and worms the forms repro-
ducing by parthenogenesis are usually larval or immature, as if they were prematurely
hurried into existence, and their reproductive organs had been elaborated in advance
of other systems of organs, for the hasty, sudden production, so to speak, of large
numbers of individuals like themselves.

In insects, dimorphism is intimately connected with agamic reproduction. Thus
the summer wingless, asexual Aphis and the perfect winged autumnal Aphis may be
called dimorphic forms. The perfect female may assume two foiins, so much so as to
be mistaken for two distinct species. Thus, an oak gall-fly {Cynips quercus-spongifica)
occurs in male and female broods in the spring, while the autumnal brood of females
was described originally as a separate species under the name C. acictdata. Walsh
considered the two sets of females as dimorphic forms, and that Ci/nips acicidata lays
eggs which produce C. quercxis-spongifica. Among butterflies, dimorphism occurs.
Papilio memnon has two kinds of females, one being tailless, like the tailless male,
while Papilio pammon is polymorphic, there being three kinds of females besides
the male.

1 THE ANIMAL KINGDOM.

There are also four forms of PapiUo aja.v, the three others being origiually
described as distinct species under the name of P. 3farcelhis, P. telamonides, and P.
walshii. Our PajyUlo glaucus is now known to be a dark, dimorphic, climatic form of
the common Papilio turnus. There are dimorphic males among certain beetles, as in
the Golofa hastata of Mexico, in which one set of males are large and have a very
large erect horn on the prothorax, and in the other the body is much smaller, with a
very short conical horn.

Tcmj)erature is also associated with the production of polymorjDhic forms in the
temperate regions of the earth, as seen in certain butterflies, southern forms being-
varieties of northern forms, and alpine ' species ' proving to be varieties or seasonal
forms of lowland species. For example, Weismann states that the Eurojjean butter-
flies, Lycaoii amyntas and 2^ohjsperchon are respectively summer and spring broods.
Anthocharis simplonica is an Aljnne winter form of Anthocharis delta, as is Pieris
bryonice of Pieris napi. In this country, as Edwards lias shown, two of the poly-
morphic forms of Papilio ajax — i. e., icalshii and telamonides — come from winter
chrysalids, and P. Marcellus from a second brood of summer chrysalids. It thus
appears that polymorphism is intimately connected with the origin of sjiecies. Per-
haps the most remarkable case of polymorphism is to be seen in the white ants ( Ter-
mites), where in one genus there are two sorts of workers, two sorts of soldiers, and
two kinds of males and females, making eight sorts of individuals ; in the other genera
there are six. Among true ants there are, besides the ordinary males, females, and
workers, large-headed workers. In the honey-aut {Myrmecocystus mexicanus), be-
sides the usual workers, there are those with enormous abdomens filled with honey.
Other insects, especially certain grasshoppers, are dimorphic. Certain parasitic nema-
tode worms are dimorphic ; and among the ccelenterates, especially the hydroids, there
is a strong tendency to polymorphism.

EVOLUTION.

In a single word — evolution — is comprised that vast complex of factors which
has resulted in the stocking of our earth with plants and animals, each after its kind.
The explanation of the process by which the life-forms of this planet have been
brought into existence is .an intricate series of problems within problems, as infinite as
is the variety in nature itself. In early ])re-scientific times, in the childhood of the race,
it seemed sufficient to say that every living thing was created, and with this statement
the majority of mankind were content to rest; not so, however, a few isolated
thinkers, who, from the time of Democritus, have questioned nature, and as earnestly
as reverently sought how these things could have come to p.ass. When geology began
to assume a definite shape; when Cuvier and L.amarck h.ad sketched out the leading
types of animal life, as Jussieu did the earth's flora ; and after paleontology began to
be a science, and it became known that the earth had been peopled by successive floras
and faunas, appeared Lamarck Jind St. Hilaire as philosophers, who combated the
cataclysmic ideas of Cuvier, and who maintained both the unity of organization of
organic beings and the immense lapse of time since the beginning of life — time
enough for the changes and adaptations needed to bring about the present condition of
things. In 1802, twenty-three years before the ajipearance of Cuvier's Discourse
Sur les Revolutions du Globe, Lam.irck uttered these striking words ; '■'■Povr la nature,
Ic temps u'est rien, et n'est jamais une difficulie ; elle Va toujours d, sa disposition, et

INTRODUCTION. li

c'est pour elle un vioyen sans homes avec lequel die fait les plus (/randes choses cotnme
les t?ioindres."

In 1809 Lamarck published his Philosophie Zoologique. This work comprised
the results of his speculations as well as of his special work of concise description,
determination, and classification of vegetable and animal species. He was struck with
the differences, but still more with the resemblances in animals ; he noticed their
variations, and, as Martins has said, a triple impression was made oti his mind : the
certainty of the variability of species under the influence of external agencies ;
that of the fundamental unity of the animal kingdom ; finally, the probability of the
successive generation of different classes of animals, arising, so to speak, one from
another, like a tree whose branches, leaves, flowers, and fruits are the results of
successive evolutions of a single organ, — the seed or bud.

All this was however speculation, a priori, premature guesses without a broad basis
of facts. The fulness of time had not yet come. The year 1809 was long ante-
rior to the general use of the microscope, before the sciences of embryology, of his-
tology, the doctrine of the cell, and before the principles of palreontology and zoo-
geography had been founded. Lamarck was almost forgotten, his speculations had
been treated with silent contempt or indifference. A jjeriod of over half a century
succeeded, an age of busy search for facts, a period prolific in inductive sciences, — a
sisterhood of knowledge as numerous as the family of Niobe. In the year 1859,
Darwin, Wallace, Bates, and among botanists. Hooker, unanimously insisted on the
fact of the variation of species and their origin by natural causes ; and they supported
their views by special more or less limited theories. Darwin's theory of natural selec-
tion was adopted with a rapidity and unanimity unjjaralleled in the history of science.
We will now examine the general argument, and state some of the general princijjles
upon which the modern scientific theory of descent is based.

There are three laws or inductions sujjporting the theory : 1. Change in the envi-
ronment of the organism, involving adaptation to such change. 2. Transmission by
heredity of ancestral together with acquired traits. 3. The selection of useful traits
and their preservation and fixity. Around each of these leading principles cluster
others accessory and indispensable, and doubtless still others may yet be discovered.

The recognition of two factors have attracted fresh attention to the theory of
descent, and caused it to be generally accepted as a working theory indispensable to
biological science ; these are (1) the facts of variation with the difficulty of limiting
species and genera, and the discovery of connecting links between the higher groups
of animals, including orders, classes, and sub-kingdoms ; and (2) the influence on the
plant or animal of a change in the environment. The second of these factors was
advocated by Lamarck and St. Hilaire. Since the publication of Darwin's special
theory of natural selection, which was accepted as a vera causa by the large propor-
tion of naturalists, a few have not been satisfied with this theory alone, but have in
various directions gone back of Darwin and natural selection to views like those of
Lamarck, whether they were acquainted with his theory and works oi- not. Darwin
took the tendency to variation as the foundation upon which to erect the superstruc-
ture of natural selection ; others have sought to account first for the tendency to varia-
tion, and then given natural selection its due place as a secondary, though important,
phase. Had Lamarck, with liis unquestioned ability as a thinker and observer, lived at
the present time, when so many new sciences have arisen, and the older ones of chem-
istry and physics have been revolutionized, he would have checked his im.agination

Hi THE ANIMAL KINGDOM.

here and there, and given us a theory well grounded on facts. It was reserved, bow-
ever, for the tireless genius of Darwin, with his masterly handling of facts, to impress
his conclusions on the age, supporting them as he did with an overwhelming array of
facts. His compactly built sujierstrueture was erected on a temporary foundation,
which it will be the work of the future to rebuild with solid masonry, resulting from cen-
turies of labor in the field first jjointed out by Lamarck. The influence of Lamarck's
work was feeble, owing to the strong counter-currents set up by Cuvier, Agassiz, and
popular prejudice.

What Lamarck actually accomplished has been restated by Charles Martins. He
noticed the variations of species, botli of animals and jilants. The best results of
his labors of over thirty years in botany, and afterwards of thirty years in zoology,
were his division of the animal kingdom into vertebi'ates and invertebrates; his
founding the classes of Infusoria and of Arachnida ; his separation of the Cirripedia
from the Mollusca, only a few years before Thompson discovered their true affinities.
Lamarck had a jjowerf ul imagination, and was a born speculator ; but the age in which he
worked was barren of facts, and many of his theories were ill-founded. The grand results
of his work were clear views as to the unity of organization of the animal kingdom,
the filiation of all animal forms, and the influence of external agencies on the varia-
tion of species ; he recognized the effects of use and disuse on the development and
atrophy of organs ; he recognized the agency of the water, of air, of light, of heat, in
bringing about changes in organisms ; finally, Lamarck was the first to construct a
phylogeny or genealogical tree of animals.

Lamarck's doctrine of .appetency w.as carried too far, and exposed his views in
general to ridicule; he maintained that spontaneous generation takes place at the
present time ; others have advocated this doctrine since Lamarck, and only within a
few years have the researches of Tyndall led him and Huxley, as well as others, to
aflirm that there is no evidence that the process is now going on.

In his famous controversies with Cuvier, Geoffrey St. Hilaire stated his belief in the
modification of species by changes in the conditions of life. As successors in Europe
may be mentioned the following writers : Wagner, Martins, and Plateau, as well as
those given below.

In Germany, the distinguished anatomist, histologist and embryologist, Kolliker,
in his ' Morphology and developmental History of Pennatulids,' published in 1872, con-
cludes as follows : " Such external forces have operated so as to modify, in many
ways, developmental processes, and no theory of descent is complete which does not
take these relations into account. Manifold external conditions, when they operate on
eggs undergoing their normal development, on larvse and other early stages of animals,
and on the adult forms, have produced in them partly progressive, partly regressive,
transformations. ... Of such external forces the most important are the mode of life
(parasitic and free-living animals, land and water animals), nutrition, light, and heat."

In his History of Creation (1873), Haeckel gives full credit to Lamarck's views, say-
ing : " Without the doctrine of filiation, the fact of organic development in general
cannot be understood. We should, therefore, for this reason alone, be forced to
accept Lamarck's theory of descent, even if we did not possess Darwin's theory of
selection." Here may also be mentioned the researches of Siebold and of Brauer, on
the effects of desiccation on the eggs of phyllopod Crustacea, and of Hogg, Dumeril,
Wyman, and others, that the metamorphosis of frogs is hastened or retarded by differ-
ences in temperature and light.

INTRODUCTION. liii

Weismann, in his suggestive work, Studies in the Theory of Descent, (1875-76),
conchides from his extended investigations on seasonal dimorjjhism, " that differences
of specific value can originate through the direct action of external conditions of life
only. ... A species is only caused to change through the influence of changing
external conditions of life, this change being in a fixed direction which entirely de-
pends on the physical nature of the varying organism, and is different in different
species or even in the two sexes of the same species."

Weismann has certainly proved that new species arise by differences in climate,
while he also (in a note to the English edition) concedes that sexual selection plays a
very important part in the markings and coloring of butterflies, but he significantly
adds, " that a change produced directly by climate may be still further increased by
sexual selection."

A second point, and one of particular interest, which the author claims to be eluci-
dated by seasonal dimorphism, is "the oiigin of variability." Having shown that
"secondary forms are for the most part considerably more variable than primary
forms," it follows that " similar external influences either induce different changes in
the different individuals of a species, or else change all individuals in the same manner,
variability arising only from the unequal time in which the individuals are exposed to
the external influence. The latter is undoubtedly the case, as appears from the differ-
ences which are shown by the various individuals of a secondary form. These are,"
he adds, giving his proofs, "always only differences of degree and not of kind." He
sliows that allied species and genera, and even entire families (Pieridte), "are
changed by similar external inducing causes in the same manner, or better, in the
same direction."

In his Ursprung und der Princip des Functionswechsel, (1875), Dr. A. Dohrn
states his belief that new habits induce the organs to exercise apparently new func-
tions, which were latent or only partly developed under the original conditions of the
surroundings.

Another work, laden with facts, with not much space wasted on theories, is Semper's
Animal Life as affected by the Natural Conditions of Existence (1877-81). This is
the first general work especially devoted to an attempt to discover the causes of
variation in animals. As the author says in his preface, "It appears to me that of all
the properties of the animal organism, variability is that which may first and most
easily be traced by exact investigation to its efficient causes ; and, as it is beyond a
doubt the subject around which at the ]iresent moment the strife of opinions is most
violent, it is that which will repay the trouble of closer research." An enumeration of
the subjects treated in the respective chapters of this work will give one an idea of the
way in which this difficult subject should be studied : food and its influence; the influ-
ence of light, of temperature, of stagnant water, of a still atmosphere, of water in
motion; currents as a means of extending or hindering tlie distribution of species, and
the influence of living organisms on animals.

In the United States a number of naturalists have advocated what may be called
neo-Lamarckian views of evolution, especially the conce])tion that in some cases rapid
evolution may occur. The present writer, contrary to pure Darwinians, believes that
many species, but more especially types of genera and families, have been produced by
changes in the environment, acting often with more or less rapidity on the organism,
resulting at times even in a new genus, or even a family type. Natural selection, act-
ing through thousands, and sometimes millions, of generations of animals and plants,

liv THE ANIMAL KINGDOM.

often operates too slowly ; there are gaps which have been, so to speak, mtentionally
left by Nature. Moreover, natural selection was, as used by some writers, more an
idea than a vera causa. Natural selection also begins with the assumption of a ten-
dency to variation, and presupposes a world already tenanted by vast numbers of ani-
mals, among which a struggle for existence was going on, and the few wei-e victorious
over the many. But the entire inadequacy of Darwinism to account for the primitive
origin of life-forms, for the original diversity in the different branches of the tree of
life-forms, the interdependence of the creation of ancient faunas and tloras on geologi-
cal revolutions, and consequent sudden changes in the environment of organisms, has
convinced us that Darwinism is Ijut one of a number of factors of a true evolution
theory ; that it comes in play only as the last term of a series of evolutionary agencies
or causes ; and that it rather accounts, as first suggested by the Duke of Argyll, for the
preservation of forms than for their origination. We may, in fact, eomjjare Darwinism
to the apex of a pyramid, the larger mass of the pyramid rejirescnting the true theory,
or complex of theories, necessary to account for the world of life as it has been and
now is. In other words, we believe in a modified and greatly extended Lamarckian-
ism, or what may be called neo-Lamarckianisiu.

It is not the design to jiresent here- arguments for this theory of evolution, but to
show what American authors have written in favor of the incidental, as well as the
periodical, recurrence of sudden or quick evolution, through changes in the environ-
ment, as opposed to the supposed continuous action of natural selection.

Without doubt, that able and philosophic naturalist, the late S. S. Haldeman, was
not unfavorable to a modified form of Lamarckian views as to the transformation of
species. His Enumeration of the recent fresh-water Mollusca vs'hich are common
to North America and Europe, with Observations on Species and their Distribution,
was published as early as January, 1844. Pie takes occasion to remark : " I pretend not
to offer an opinion for or against tlie Lamarckian, being more anxious to show the in-
sufficiency of the standing arguments against it, and the necessity of a thorough
revision of them, than to take a decided stand (upon a question which I regard as open
to farther discussion) before its facts h.ive been carefully observed, or the resulting gen-
eralizations properly deduced ; so that, whether it be admitted or not, it is entitled to
the benefit of all the discoveries which can be brought to bear upon it ; and, on this
account, I have not hesitated to give a slight sketch of the theory of transmutation, as
I conceive it to be modified b_v some of the results of modern science."

In the course of his essay he remarks: "The reason why the lower orders still
exist is to be looked for in the fact that they are fitted for the circumstances under
which we find them." Again ho s.ays : " Altliough we may not be able, artificially, to
produce a change beyond a definite jiohit, it would l)e a hasty inference to suppose thiit
a physical agent, acting gradually for ages, could not carry tlie variation a stejt or two
f.arther ; so that, instead of the original, we will say four varieties, they might amount
to six, the sixth lieing sufficiently unlike the earlier ones to induce a naturalist to con-
sider it distinct. It will now have reached the limit of its ability to exist as the former
species, and must be readj- either to develojj a dormant organic element, or die ; if the
former is effected, the oscillating point is passed, and the species established upon the
few individuals that were able to survive the shock. If the physical revolution suji-
posed to lie going forward is arrested, or recedes, the individuals which had not passed
the culminating point remain as a fifth variety, or relapse towards their former station ;
whilst the few which linve crossed the barrier remain permanently beyond it, even

INTRODUCTION. Iv

under a partial retrogression of the causes to which they owed their newly developed
organization."

Very significant is tlie suggestion which follows, as to the cause of comparatively
sudden leaps in the process of evolution : We may suppose some species and indi-
viduals to be more able to pass than others, and that many become extinct from ina-
bility to accomplish it. Under this point of view, a hiatus, rather than a regular
passage, is required between a species and that whence it is supposed to be derived,
just as two crystals may occur, nearly identical in composition, but without an insensi-
ble gradation of intermediate forms ; the laws, both of organic and inorganic matter,
requiring something definite, whence the rarity of hybrids and monsters, themselves
subject to established laws." He adds, in a foot-note : " The same mineral may crys-
talize with three, six, or twelve angles, but not with five or seven. Are the phases of
organic morphism subject to less definite laws?"

In the year 1850, Professor Joseph Leidy wrote that a slight modification of the
essential conditions of life were sufficient to produce the vast variety of living beings
upon the globe.

In 1853 Dr. Jeffries Wyman published a paper on the effect of the absence of light
on the development of tadpoles, and in 18G7 appeared his Observations and Experi-
ments on Living Organisms in Heated Water. Professor Wyman taught the doctrine
of evolution as early as 1861, and probably earlier.

In 1864 B. D. Walsh endeavored to establish the fact that, while the great majority
of species may have been formed by natural selection, some originated "by changes in
the conditions of life, and especially by change of food." H. J. Clark, in his Mind
and Nature (1865), advocated evolution, and even spontaneous generation through
physical processes.

Professor Alpheus Hyatt (in 1866) showed that the development of the individual
in the Ammonites agrees with the development of the order to which it belongs, and
he afterward showed, by a study of Ammonites of different geological formations, that
just as there ai-e sudden changes of form in the growth of the individual, so species and
genera of one formation replace those of another, in such a manner that one form
must have descended from the other, although the differences between the forms are
very marked.

In 1869 Professor E. D. Cope, in his essay on the Origin of Genera, suggested
that, by an acceleration or retardation in the development of the animal, generic forms
had been produced. He claimed that, " while natural selection operates by the ' preser-
vation of the fittest,' retardation and acceler.ation act without any reference to ' fitness'
at all ; that, instead of being controlled by fitness, it is the controller of fitness." He
also remarks that the "transformations of genera may have been rapid and abrupt,
and the intervening periods of persistency very long; " in other words (p. 80), genera
and higher categories have appeared " in geological history by more or less abrupt
transitions, or expression points, rather than by uniformly gradual successions."

It should be observed, however, that Cope clid not enter into the causes which
produce acceleration and retardation, but in later papers he has extended and more
fully stated his views.

Marsh's observations, published in 1868, on the transformtion of Siredon into the
ordinary gill-less salamander (Ambli/stoma), was a step in the same direction, *. e. giving
proofs of rapid change in the acquisition of new organs, and modifications of existing
ones.

liv THE ANIMAL KINGDOM.

often operates too slowly ; there are gaps which have been, so to speak, intentionally
left by Nature. Moreover, natural selection was, as used by some writers, more an
idea than a vera causa. Natural selection also begins with the assumption of a ten-
dency to variation, and presupposes a world already tenanted by vast numbers of ani-
mals, among which a struggle for existence was going on, and the few were victorious
over the many. But the entire inadequacy of Darwinism to account for the primitive
origin of life-forms, for the original diversity in the different branches of the tree of
life-forms, the interdependence of the creation of ancient faunas and floras on geologi-
cal revolutions, and consequent sudden changes in the environment of organisms, has
convinced us that Darwinism is but one of a number of factors of a true evolution
theory ; that it comes in play only as the last term of a series of evolutionary agencies
or causes ; and that it rather accounts, as first suggested by the Duke of Argyll, for the
preservation of forms than for their origination. We may, in fact, compare Darwinism
to the apex of a pyramid, the larger mass of the pyramid representing the true theory,
or complex of theories, necessary to account for the world of life as it has been and
now is. In other words, we believe in a modified and greatly extended Lamarckian-
ism, or what may be called neo-Lamarckianism.

It is not the design to present here- arguments for this theory of evolution, Init to
show what American authors have written in favor of the incidental, as well as the
periodical, recurrence of sudden or quick evolution, through changes in the environ-
ment, as opposed to the supposed continuous action of natural selection.

Without doubt, that able and philosophic naturalist, the late S. S. Haldeman, was
not unfavorable to a modified form of Lamarckian views as to the transformation of
species. His Enumeration of the recent fresli-water Mollusca which are common
to North America and Europe, with Observations on Species .and their Distribution,
was published as early as January, 1844. He takes occasion to remark : " I jjretend not
to offer an opinion for or against the Lamarckian, being more anxious to show the in-
sufficiency of the standing arguments against it, and the necessity of a thorough
revision of them, than to take a decided stand (upon a question which I regard as open
to farther discussion) before its facts have been carefully observed, or the resulting gen-
eralizations proj)erly deduced ; so that, whether it be admitted or not, it is entitled to
the benefit of all the discoveries which can be brought to bear upon it ; and, on this
account, I have not hesitated to give a slight sketch of the theory of transmutation, as
I conceive it to be modified by some of the results of modern science."

In the course of his essay he remarks: "The reason why the lower orders still
exist is to be looked for in the fact th.at they are fitted for the circumstances under
which we find them." Again he says : " Although we may not be able, artificially, to
produce a change beyond a definite point, it would be a hasty inference to sujipose that
a ]3hysical agent, acting gi-adually for ages, could not carry the variation a step or two
farther; so that, instead of the original, we will say four varieties, they might amount
to six, the sixth being sufficiently unlike the earlier ones to induce a naturalist to con-
sider it distinct. It will now have reached the limit of its ability to exist as the former
species, and must be ready either to develop a dormant organic element, or die ; if the
former is effected, the oscillating point is passed, and the species established upon the
few individuals that were able to survive the shock. If the physical revolution sup-
posed to be going forward is arrested, or recedes, the individuals which had not passed
the culminating point remain as a fifth variety, or rela]ise towards their former station ;
whilst the few which have crossed the barrier remain pennanently beyond it, even

INTRODUCTION. Iv

under a partial retrogression of the causes to which they owed their uewly developed
organization."

Very significant is the suggestion which follows, as to the cause of comparatively
sudden leaps in the process of evolution : We may suppose some species and indi-
viduals to be more able to pass than others, and that many become extinct from ina-
bility to accomplish it. Under this point of view, a hiatus, rather than a regidar
passage, is required between a species and that whence it is supposed to be derived,
just as two crystals may occur, nearly identical in composition, but witliout an insensi-
ble gradation of intermediate forms ; the laws, both of organic and inorganic matter,
requiring something definite, whence the rarity of hybrids and monsters, themselves
subject to established laws." He adds, in a foot-note : " The same mineral may crys-
talize with three, six, or twelve angles, but not with five or seven. Are tlie phases of
organic morphism subject to less definite laws?"

In the year 1850, Professor Joseph Leidy wrote that a slight modification of the
essential conditions of life were sufficient to produce the vast variety of living beings
upon the globe.

In 1853 Dr. Jeffries Wyman published a paper on the effect of the absence of light
on the development of tadpoles, and in 1867 appeared his Observations and Experi-
ments on Living Organisms in Heated Water. Professor Wyman taught the doctrine
of evolution as early as 1861, and probably earlier.

In 1864 B. D. Walsh endeavored to establish the fact that, while the great majority
of species may have been formed by natural selection, some originated " by changes in
the conditions of life, and especially by change of food." H. J. Clai-k, in his ]\Iind
and Nature (1865), advocated evolution, and even spontaneous generation through
physical processes.

Professor Alpheus Hyatt (in 1866) showed that the development of the individual
in the Ammonites agrees with the development of the order to which it belongs, and
he afterward showed, by a study of Ammonites of different geological formations, that
just as there are sudden changes of form in tlie growth of the individual, so species and
genera of one formation replace those of another, in such a manner that one form
must have descended from the other, although the differences between the forms are
very marked.

In 1869 Professor E. D. Cope, in his essay on the Origin of Genera, suggested
that, by an acceleration or retardation in tlie development of the animal, generic forms
had been produced. He claimed that, " while natural selection operates by the ' preser-
vation of the fittest,' retardation and acceleration act without any reference to ' fitness '
at all ; that, instead of being controlled by fitness, it is the controller of fitness." He
also remarks that the "transformations of genera may have been rapid and abrupt,
and the intervening periods of persistency very long;" in other words (p. 80), genera
and liigher categories have appeared "in geological history by more or less abrupt
transitions, or expression points, rather than by uniformly gradual successions."

It should be observed, however, that Cope did not enter into the causes which
produce acceleration and retardation, but in later papers he has extended and more
fully stated his views.

Marsh's observations, pulilished in 1868, on the transformtion of Siredon into the
ordinary gill-less salamander (AmhlyMotiHi), was a step in the same direction, *. e. giving
proofs of rapid change in the acquisition of new organs, and modifications of existing
ones.

Ivi THE ANIMAL KINGDOM.

In The American Naturalist, for December, 1871, the writer assumed, from a
study of cave animals, that these forms were suddenly produced, though the changes
may not have been wrought until, say, after several thousand generations; and the theory
of Cope and of Hyatt, of creation by a process involving the idea of accelerated de-
velopment in some species, and retarded development in certain organs of other species,
was adopted. These views were again enforced in Hayden's Bulletin of the United
States Geological Survey (April, 1877), in an article on the Cave Fauna of Utah.

In 1872 the writer (Development of Limulus), from a study of the paleozoic
Crustacea and of the develoinneut of Limulus, claimed that it was impossible " that
at the dawn of silurian life these well-marked groups were due entirely to the extinc-
tion of multitudes of connecting links, such as Mr. Darwin assumes to have been
evolved on the jirinciple of natural selection, with the subordinate agency of sexual
selection and mimicry, etc. The groups are almost as clearly marked as in the present
time, and such a theory seems to us inadequate to account for the rise of such distinct
forms, apparently simultaneous in their appearance at the beginning of the silurian.
The forms are remarkably isolated, and present every appearance of having been in a
degree suddenly produced," i. e., by differences in the temperature and depth of the
water, etc., the differences being due to changes in the jihysical surroundings of the
organisms. Farther on it is stated : " I conceive these differences to be due, perhajis,
to sudden changes of temperature in fresh-water pools, to the difference in the density
of fresh and salt water, and the liability of fresh-water pools to dry up, combined with
less apparent causes." It will be seen that these views essentially agree with what is
known as Lamarckianism. In his Monograph of the Geometrid Moths, the writer
attempted to show that climatic and geological causes were important factors in the
production of the genera and species constituting the different faunas.

That changes in the physical surroundings of the organism, rather than the strug-
gle for existence among the animals themselves, produce new forms of animal life,
was also insisted upon by the writer (Half Hours with Insects, 1876), in the follow-
ing words : —

" When one looks at the beds of fossil beings of the earlier geologic periods, he
peers into the tombs of millions which could not adapt themselves to their constantly
changing surroimdings. No fossil being is known to us which could not have been as
well adapted to its mode of life as the animals now living ; but the conditions of life
changed, and the species, as such, could not withstand the possible influx of new forms,
due to some geological change which induced emigration fi-om adjoining territories, or
to changes of the contour of the surface, with corresponding climatic alterations.
Let one look at the geological map of North America before the cretaceous period,
ere the Rocky Mountains appeared aliove the sea, and reflect on the remarkable changes
that took place to the northward, — the disappearance of an Arctic continent, the re-
placement of a tropical climate in Greenland and Spitzbergen by Arctic cold. Are
there not here changes enough in the physical aspects of our country to warrant such
hypotheses of migrations, with corresponding extinctions and creations of new faunas
out of preceding ones, as are indulged in by naturalists of the present day, in the light
of the knowledge pouring in upon them from Arctic explorers and western geologists?
Granted these extraordinary changes in the jthysical surroundings of the animals
whose descendants people our land, do not a host of questions arise as to the result, in
the beings of our day, of these changes in the modes of life, the modes of thought, so
to speak, the formation of peculiar instincts arising from new exigencies of life, which

INTRODUCTION. Ivii

have remodelled the whole psychology, as it were, of the animals of our country?
Instincts vary with the varying structure and form of the animals. Change the sur-
roundings, and at once the mode of life and psychology of the organism begin to
undergo a revolution. These changes may result in the gradual extinction of whole
assemblages of animals, which are as gradually replaced by new faunas."

Mr. J. A. Allen has (in his works on the variation of birds, published in 1871, and
especially in subsequent papers) shown the influence of climate and temjierature in
directly inducing specific changes, without the agency of natural selection.

In the American Naturalist for March, 1877, Mr. W. H. Dall published a thought-
ful article On a Provisional Hypothesis of Saltatory Evolution. He realizes that
" leaps, gaps, saltations, or whatever they may be called, do occur " in the evolution of
forms. Mr. Dall remarks that " the apparent leaps which Nature occasionally exhibits
may still be perfectly in accordance with the view that all change is by minute differ-
ences, gradually accumulated, in response to the environment."

The articles of Mr. W. H. Edwards on dimorphism and seasonal variation in our
butterflies (Canadian Entomologist, 1877) throw light on the production of species by
climatic changes, and, with Weismann's work on this subject, published in Germany,
clearly show how many species were called into being by the geological and especially
climatic changes wrought by the advent and departure of the glacial period. All
these works show how many are the causes, much more fundamental than natural
selection, which have played their part in the origin of the varieties, which have been,
however, preserved by natural selection.

In his work on sponges (published May, 1877) Professor Hyatt gives a large
number of novel facts, showing how greatly sponges are modified in form by the nature
of the sea-bottom and the temperature of the water. The same line of thought is
extended in his elaborate treatise on the Steinheim shells, published in 1882.

It should also be said that Huxley has incidentally observed : " We greatly susi^ect
that Nature does make considerable jumps in the way of variation now and then, and
that these saltations give rise to some of the ga]is which appear to exist in the series
of known forms." Galton, Mivart, and W. K. Brooks have also favored the view that
saltations may occur.

Two recent addresses, one by Professor Le Conte of California, and the other by
Mr. Clarence King (1877), have forcibly set forth the results upon organic life of the
revolutions in the history of the earth. Professor Le Conte, speaking as a geologist,
represents " the organic kingdom as lying, as it were, passive and plastic under the
moulding hands of the environment." He speaks of "general evolution, changes
of organisms, whether slow or rapid, as produced by varying pressure of external
conditions." Again, he ably remarks : " There seems good reason to believe that the
evolution of the organic kingdom, like the evolution of society, and even of the
indiviilual, has its periods of rapid movement and its periods of comparative repose
and readjustment of equilibrium." He illustrates this by referring to the change from
the cretaceous to the tertiary period, involving not only a change in climate, but of
salt water to fresh, and the extinction of some marine animals, as well as the transmu-
tation of others into fresh-water species. Le Conte gives the first place to pressure on
the organism resulting from changed physical conditions, and the second place to
natural selection.

Mr. Clarence King, with his experience as a geologist in the west, has advocated
catastrophism in geology, and shows the inadequacy of uniformitarianism in entirely

Iviii THE ANIMAL KINGDOM.

accounting foi- the epochs of the earth's history, and he discusses the results of such
catastrophic views on evohition.

Returning to the consideration of the three factors or fundamental causes bringing
about a tendency to variation, we may first consider the clianges in the relative distri-
bution of land and sea. Geological history is an epitome of the wide-spread and long-
continued changes in the shape of the continents, from the time when, as Laurentian
land-masses, there appeared but isolated nuclei of what are now the continents. Geol-
ogy shows that these pi-imeval incipient continents were original centres of creation,
and that however contiguous continents may have borrowed one another's features,
whether to a limited or wide extent, yet, notwithstanding a nearly uniform tempera-
ture and climate, the evolution and specialization of life-forms went on throughout
the different growing continents, resulting in the zoo-geographical realms of the
present day. Here also should be taken into account the elevation of the Hima-
layas, the Cordilleras of America, and tlie Alps and other high mountain chains,
producing circumscribed areas, with different climates and other geographical fea-
tures.

Finally came the Ice period, with the division of the earth's temperature into tor-
rid, temperate, and frigid zones. The changes in the animals and plants resulting from
these events must evidently have brought about (1) the extinction of many older types,
those unfitted for the new conditions of life ; (2) the modification of others more
plastic and endowed with greater vitality, while (3) a few forms, such as Lingula,
Ceratodus, etc., endowed with still greater vitality, persisted from early times till now.
They were the sole survivors of changes in physical conditions and of a wreckage of
life-forms, whose remains fill the cemeteries of paleozoic, mesozoic, and tertiary times.

Geological history also shows that there have been periods of long preparation,
marked by oscillations of continents, finally terminating in crises. Examples are the
accumulations of sediments, their upheaval, metamorphism, and conversion into the
Alleghanies, which marked the end of the paleozoic era in eastern North America.
The processes of contineut-makhig went on in the eastern hemisphere, beginning at
the time when Europe was an archipelago and ending with the period when these
islands became united, and Europe and Asia were consolidated into a single continent.

The crises in organic life, the origin, rise, culmination, and final extinction of types
of organic life, went hand in hand with these great changes in the physical geography
of our earth, as seen in the history of the trilobites, of the brachiopods, of the N eba-
lids, the Eurypterids, the Dipnoans, and the Labyrinthodonts, etc. ; and among plants,
the Lepidodendrons, Calamites, Sigillarias, and other extinct forms.

Finally, the embryological development and metamorphosis of animals often have
a most significant meaning, being condensed histories of changes which must have
occurred in the history of their type in past ages. The generalized appearance of the
embryo is paralleled by the generalized condition of paleozoic tyjies and their present
survivors ; the sudden assumption of special characters at or just before the time of
birth, is paralleled by the great specialization in form and structure which went on
throughout the world in the mesozoic and tertiary times, when forests of club mosses,
giant Equiseta, and synthetic, broad-leaved conifers, gave way to growths of modern
pines and oaks, beeches, willows, pojjlars, maples, ami nther hard-wood trees; while
among animals thousands of species of bony fishes, and the whole class of mammals, re-
placed the generalized quadrujjedal back-boned creatures which haunted the carbon-
iferous forests — orowths of dld-fasliioned tree-ferns and club-mosses, with not a flower-

INTRODUCTION. IJX

ing herb or tree to relieve tlie monotony of the rank, weedy, colossal, but unfinished
plants clothing the hills and jjlains of those days.

Thus the whole course of development was from crude, chaotic, generalized
forms, both animal and plant, to more elaborate, highly-finished, or specialized forms ;
this progress towards higher and better things biological going on hand in hand with
progress in continent-building, the elaboration of lowlands, plateaus, and mountain
chains, until, in the fulness of time, the whole creation revels in marvels of beauty,
in a variety so beautiful and delicate as to appeal to the esthetic tastes and to form a
training-school in the good, the beautiful, and true for the last product of evolution,
that being who has been endowed with sufficient intelligence to read the history of
creation, and to look up beyond and abo\e the material world to the Infinite Source of
all the pihysical and evolutional forces which have made the universe.

The facts and inductions we have hastily glanced at were established before Dar-
win published his Origin of Species. The interpretation now given to them is
mainly due to Iiini, who has shown their full significance. As full proofs, however, are
the facts regarding the conditions of existence which have been mostly collected by
those to whose works we have already referred. These, in the main, are the influence
of light or its absence, temperature, parasitism, etc.

The study of the effect of these physical agents on organisms is still in its infancy;
the facts can best be observed in external nature, and experimentally in the laboratory.
As the result, however, of known facts, it seems evident that the causes of variation,
manifold as they seem to be, are such as to- be appreciated by the patient and careful
observer, and this is the direction which biological research is now taking. Changes
in the environment and adaptation to such changes as these, then, are the fundamental
causes of the origin of new forms of life.

The next factor is the transmission to the offspring of changes thus induced, and
to which the organism has become in a slight degree adapted. Tiiis is heredity.

Of the causes of heredity we know almost nothing. The solution of the problem
belongs to the future. The facts are witnessed by every human being. All organisms
transmit their own jieculiarities as well as those of their race, variety, species, genus,
or class to their offspring. Heredity is seen externally in the general shape of the
body or trunk, whether stout or slender ; in the head and in the limbs, even in the
nails and hair, also in the human countenance, in the expression or characteristic fea-
tures, as well as in the skin. The Romans, says Ribot, had their Nasones, Labeones,
Buccones, Capitones, and other names derived from hereditary peculiarities. Internal
peculiarities, such as the shape and size of the bones of the skeleton, and especially
the skull and teeth, are hereditary, and even, says Lucas, the heredity of excess or de-
fect in the number of the vertebra? and the teeth has been observed. The circulatory,
digestive, muscular, and nervous systems obey the same laws, which also govern the
transmission of the other internal systems of the organism. There are some families,
says Ribot, in which the heart and the size of the princii)al blood-vessels are naturally
very large ; others in which they are comparatively small; and others, again, which
present identical faults of conformation. The general dimensions of the brain, and
even the size and form of the cerebral convolutions, as observed by Gall, are hereditary,
and this author in this way accounted for the transmission of mental faculties. Pecu-
liarities in the blood-vessels and the blood itself may be transmitted, as seen in the ten-
dency in certain families to apoplexy, haemorrhages, and inflammatory diseases.
Length of life, fecundity or the opposite trait, is hereditai'y. In some families the hair

Ix THE ANIMAL KINGDOM.

turns gray in early life ; immunity from small-pox in some families is said to be a well-
establislied fact ; muscular strength, as seen in running, wrestling, and boating, as well
as dancing, singing, lisping, loquacity and its opposite, and peculiarities in penniansliip
and even certain habits besides various physical defects are more or less hereditary ;
and artificial deformities, such as flat heads in the North American Indians, while the
peculiar methods practised by certain Peruvian tribes, the Aymaras, the Huancas, and
the Cliinchas, respectively, are known to have been transmitted. Yet there are many
excejitions to the law of heredity, especially as i-egards temporary and accidental modifi-
cations, such as circumcision, etc. As a rule, however, not only physical but mental
characteristics may be hereditary ; of the latter class are instincts and the senses of color,
touch, light, hearing, smell, taste. A strong or weak memory is hereditary ; so also a
weak or powerful imagination, peculiarities of intellect, a violent temper or mild dis-
position, a strong or weak will, and finally idiocy or genius may run in families.

In short, no vital phenomenon, physical or mental, is exempt from the law of hered-
ity, yet there are known exceptions, and by care in breeding the domestic animals, as
is well known, physical and moral defects can be eliminated, and in mankind good
judgment in marriage may result in visible improvement in the stock of certain
families.

While the causes of heredity are unknown, attempts to account for them have been
made by various writers. Says Haeckel : " The cause of heredity is the partial iden-
tity of the materials which constitute the organism of the parent and child, and the
division of this substance at the time of reproduction." " Heredity," adds Ribot, " in
fact, is to be considered only as a kind of gi-owth, like the spontaneous division of a
unicellular plant of the simplest organization." It is evident that in some of the con-
ditions of growth we may find an explanation of the fact of heredity. Another phys-
ical theory is that of ' pangenesis ' as proposed by Darwin, who conceives that cells,
before their conversion into 'form material,' throw off minute atoms which he calls
' gemmules,' and which " may be transmitted from the parent to the offspring," and as
he claims, "are generally developed in the generation which immediately succeeds,
but are often transmitted in a dormant state during many generations and are then de-
veloped." Darwin's gemmules are entirely hypothetical, and, as Galton has observed,
the simple experiment of the transfusion of blood, by which a number of ' gemmules'
would be inevitably transmitted from one individual to another without the usual
results as regards heredity, would seem to prove that pangenesis is " incorrect." Prof.
W. K. Brooks has, in his work on Heredity, restated the hypothesis, as he claims, " in a
form which is so modified as to escape this objection."

Intimately connected with the subject of heredity is the fact of reversion or atavism,
where a child or young of any animal presents peculiarities evidently inherited not
from its parents, l3ut from its grandparent or a remoter ancestor. Cases in point are
the occasional appearance, in horses, of stripes on the body and legs, which are supposed
by Darwin to have descended from a striped zebra-like ancestor. Darwin gives other
examples, and in human families certain traits are known to have jumped over one gen-
eration and to descend to the next. It is also a matter of observation that domestic
animals allowed to run wild tend to revert to their former feral condition.

The third factor in evolution is 'natural selection.' Since the time of Laban,
hei'dsmen and stock-raisers have been able, by careful selection, matching those
cattle, horses, sheep, dogs, etc., which are pre-eminent in desirable qualities, such as
speed, size, draft, or, in the case of cows, good milking, either in quality or quantity,

INTRODUCTION. Ixi

to produce strains noticeable for this or that peculiarity useful to their owners. Dar-
win applied this law to animals and plants existing in a state of nature, i. e., wild or
uncultivated ; and claimed that a process of natural selection is going on throughout
the world. This phase of evolution is called 'Darwinism.' The work entitled The
Origin of Species, comprising the results of thirty years of observation and reflec-
tion, was published to support and confirm this special theory.

We will give a condensed statement of the theory of natural selection, from the
author's own recapitulation of his views, presented at the end of his work (fifth
edition, 1871), often using his own words. Domestic aniinals vary greatly, as the
result of changed conditions of life. " This variability is governed by many complex
laws — by correlation, by use and disuse, and by the definite action of the surround-
ing conditions." " Man does not actually produce variability; he only unintentionally
exposes organic beings to new conditions of life, and then nature acts on the organi-
zation and causes variability." "There is no obvious reason why the principles which
have acted so efficiently under domestication should not act under Nature. In the
survival of favored individuals and races, during the constantly recurring struggle for
existence, we see a powerful .and ever-acting form of selection. . . . More individuals
are born than can possibly survive. ... As the individuals of the same species come
in all respects into the closest competition with each other, the struggle will generally
be most severe between tliera ; it will be almost equally severe between the varieties
of the same species, and next in severity between the species of the same genus. On
the other hand, the struggle will often be vei-y severe between beings remote in the
scale of nature."

"With animals having separated sexes, there will be in most cases a struggle
between the males for the possession of the females. The most vigorous males, or
those which have most successfully struggled with their conditions of life, will gener-
ally leave most progeny. But success will often depend on the males having special
weapons or means of defence, or charms ; and a slight advantage will lead to victory."

He then claims that, as geology shows that each land has undergone great physical
changes, we might have expected to find that organic beings have varied under Nature
in the same way as they have varied under domestication. " If, then," he says, "ani-
mals and plants do vary, let it be ever so little or so slowly, why should we doubt that
the variations or individual differences, which are in any way benefici.al, would be
preserved and accumulated through natural selection, or the survival of the fittest? If
man can by patience select variations useful to him, why, under changing and complex
conditions of life, should not variations useful to Nature's living products often arise,
and be preserved cr selected."

It is impossible, without the evolution theory, to explain the meaning of rudimen-
tary oi-gans. " Disuse, aided sometimes by natural selection, has often reduced organs,
when they have become useless under changed habits or conditions of life ; and we
can clearly understand on this view the meaning of rudimentary organs. But disuse
and selection will generally act on each creature when it has come to maturity, and
has to play its full part in the struggle for existence, and will thus have little power
on an organ during early life : hence the organ will not be reduced or rendered rudi-
mentary at this early age. The calf, for instance, has inherited teeth which never cut
through the gums of the upper jaw from an early progenitor having well-developed
teeth ; and we may believe that the teeth in the mature animal were reduced, during
successive generations, by disuse, or by the tong\ie and palate or lips having become

Ixii THE ANIMAL KINGDOM.

better fitted by natural selection to browse without their aid ; whereas, in the calf, the
teeth have been left untouched by selection or disuse, and, on the principle of inheri-
tance at corresponding ages, have been inherited from a remote period to tlie present
day. On the view of each organic being, with all its separate parts, having been
specially created, how utterly inexplicable it is that organs bearing the plain stamp of
inutility, such as the teeth in the embryonic calf, or the shrivelled wings under the
soldered wing-covers of many beetles, should so frequently occur ! Nature may be
said to have taken pains to reveal her scheme of modification by means of rudimen-
tary organs, embryological, and homological structures, but we wilfully will not
understand the scheme."

We will finally quote the very noble words with which Darwin concludes this
volume : " There is grandeur in this view of life, with its several powers, having been
originally breathed by the Creator into a few forms, or into one ; and that, while this
planet has gone cycling on according to the fixed law of gravity, from so simple a
beginning, endless forms most beautiful and most wonderful have been and are being
evolved."

HISTORY OF ZOOLOGY.

Zoology as a descrijjtive science dates from the time of Linnreus, the father
of natural history, but as a well-grounded science it is scarcely older than 1839,
the date of Schwann's work on the cell, and the period of the manufacture and wide-
spread use of good compound microscopes. After the descriptive era of Linn»us
and his successors, arose the era of comparative anatomy and paleontology, twin branches
of biology, engrafted by Cuvier on the tree of zoological knowledge, which was planted,
so to speak, by Linnaeus. Then arose the branches of histology, embryology, and gen-
eral morphology.

The predecessors of Linnaeus, or Carl von Linne, were Malphigi, Leeuwenhoek,
Swammerdam, and Redi, who flourished before Linnreus was born (1707). Before the
birth of Linnfeus, also, there was a general scientific renaissance, which resulted in the
foundation of academies of science ; the oldest German scientific society being the
Academia Naturse Curiosorum, founded at Halle in 1652. Ten years later (1662),
the Royal Society of London was founded. Li France, Richeheu founded, as early as
1633, the Academic Fran9aise for the promotion of the French language and litera-
ture ; in the reign of Louis XIV. the Academic des Sciences was founded ; its first
volume of works bears the imprint Paris, 1671. Three other academies were estab-
lished in Paris, and the five were united under the name of the Institute Fran5ais.
Then followed the founding of the scientific societies and academies of Berlin (1700),
LTpsala (1720), St. Petersburg (1725), Stockholm (1739), Copenhagen (1743), and
Bologna, whose Commentaries first appeai-ed in 1731.

The history of zoology may be roughly divided into several periods : —

1. Period of systematic zoology. — While it should not be forgotten that Aristotle
gave the name Mollusca to the group still bearing that name, no naturalist of mark
arose until Linnreus was born. In England, Linnreus was preceded by Ray, but bi-
nomial nomenclature and the first genuine classification of animals dates back to the
Systema Naturte, the tenth edition of which appeared in 1758. As the result of his
influence, his own pupils, and also the German traveller and naturalist Pallas, did
much to advance zoo-geography; while the anatomists and physiologists of this period
were Camper, Spallanzani, Wolff, Hunter, and Vicq d'Azyr, the last-mentioned author
being the first to propose the term ' comparative anatomy.'

INTRODUCTION. Ixiii

2. Period of comparative anatomy ami paleontology. — Cuvier, born in 17G9, was
the founder of the twin sciences of comparative anatomy and paleontology, and at
Paris centred the great lights of comparative anatomy, Geoffrey Saint-Hilaire, La-
marck, Bichat, Vicq d'Azyr, Blainville ; France then leading the scientific world,
though Germany had her Blumenbach, Dollinger, Tiedemann, Bojanus, and Carus.

Meckel, at his time the leading German anatomist and compiler, studied at Paris
with Cuvier, and so did Richard Owen of England, and Milne-Edwards of France.
Both the latter are still living. Sir Richard Owen, in his eightieth year, being still
prolific in monographic memoirs, both morphological and paleonlological. Among
writers on the doctrine of animal types, who flourished in the first third of the ])resent
century, were Lamarck, Cuvier, Blainville, and Von Baer. During this period the
science of embryology began to take form under the inspiration of Oken, Pander,
Dollinger, Yon Baer, Rathke, and Wolff ; this work was carried on in later years by
Coste, Bischoff, Reichevt, Kiilliker, Vogt, and Agassiz.

The great activity shown at Paris by Cuvier in the building up of the Jardin des
Plantes, led to the French exploring expeditions sent out from 1800-1832 to all
parts of the world, resulting in enlarged views regarding the number and distribution
of species, and their relations to their environment. The zoologists who went on these
expeditions were Bory de St. Vincent, Savigny, Peron, Lesueur, Quoy, Gaimard, Vail-
lant, Eydoux, and Souleyet. From 1823-1850 England fitted out exploring expedi-
tions under Beechey, Fitzroy, Belciier, Ross, Franklin, and Stanley, the naturalists of
which were Bennett, Owen, Darwin, Adams, and Huxley.

Russia (1803-1829) sent out expeditions to the north and northeast, accomjianied
by the naturalists Tilesius, Langsdorff, Chamisso, Eschscholtz, and Brandt, all of them
of German birth and education. The United States exploring expedition under Wilkes
(1838-1842) was, in scientific results, not inferior to any previous ones, the zoolo-
gists being Dana, Conthuoy, and Peale. Of a later voyage under Ringgold, Stimj)son
was the naturalist, but the rich final results were lost by fire. At or near the close of
this pei-iod, from Germany, Humboldt, Spix, Prince Wied-Neeuwied, Natterer, Peity,
Reugger, Tschudi, Schomburgk, Burmeister; from France, de Azara, d'Orbigny, Gay,
Castlenau ; and from Denmark, Lund, — travelled at their private expense, an evidence
of the spirit of scientific research then dominating the centres of civilization. Their
followers in the present time have been Wallace, Semper, Bates, Michlucho-Maclay,
Prezvalskjr, and many others.

Towards the middle of the century, the leading comparative anatomist and ]ihysi-
ologist was Miiller of Berlin. Now began to dawn the modern period of morphology
and embryology, under his inspiration, and that of Savigny, Sars, Rathke, Agassiz.

General text-books on comparative anatomy, compiled by leading authorities, are
R. E. Grant's Lectures on Comparative Anatomy (1833-4), Wagner's (1834-5),
Owen's Lectures on the Comparative Anatomy of the Invertebrates (1843 and 1855),
and Anatomy of Vertebrates (1866-68); Siebold (invertebrates) and Stannius (verte-
brates) (1845-46); Rolleston's Forms of Animal Life (1870) ; Huxley's Anatomy of
the Vertebrates (1871), and Invertebrates (1877); finally the list culminates in the
suggestive work of Gegenbaar (1874), entitled Elements of Comparative Anatomy,
and written from the modern morphological and evolutional standpoint. The lead-
ing text-books of systematic zoology are those of Van der Hoeven (1850), Carus,
and Gerstaecker (1863-75), and lastly that of Claus (1868-84). The great eucyclo-
pa?(lic work, Classen und Ordnungcn der Thierreichs, planned and begun b^' Bronn,

Ixiv THE ANIMAL KINGDOM.

and continued by Gerstaecker, Hoffmann, Giebel, Hubrecht, Vosmaer, Biitschli, and
otliers, is a fitting embodiment of the results of higher zoological studies from Lin-
naeus to the present time.

3. Period of Morphology and Embryology. — This period has been distinguished
(1) by the application of the discovery by Schwann of the cellular theory of organized
beings, especially to animals, and the studies of Dujardin and W. Schultze on the nature
of protoplasm, proving that the cell is the unit of organization, and that protoplasm
is the basis of life ; (2) by the application of histological discoveries and methods to
embryological research, and (3) by the application of the doctrine of evolution as a
working theory to account for the common origin of animals from a single simple
organism. If single names are to be mentioned whei-e in fact many have worked
together to accomjilish these results, the names of Schwann, of Dujardin and
Schultze, and that of Darwin come first to mind.

In 1665 Robert Hooka distinguished the cells of plants, calling them "cells and
pores," and comparing them to honey-comb. Schwann was the first to discover
animal cells. Schwann first (1839) called tlie nucleus ' korperclien,' but Valentine
in the same year (1839) invented the terms nucleus and nucleolus, since then in uni-
versal use, and Valentine was the first, in his review of Schwann's work in the
Repertorium for 1839, to speak of 'the cellular theory.'

In Carnoy's La Biologic Cellulaire (1884) we find a convenient summary of the
history of the discovery of protojolasm and the doctrine that it forms the living matter
common to vegetable and animal cells. In 1835 Dujardin thus characterized this
substance : " I propose to name sarcode that which other observers have called a
living jelly, this glutinou.s, transparent, homogeneous substance, which refracts light
a little more readily than water, but much less than oil ; which is extensible and can
stretch itself like mucus, is elastic and contractile, is susceptible of spontaneously
forming spherical cavities or vacuoles, filled with the surrounding liquid, which some-
times forms of it an open network. . . . Sarcode is insoluble in water ; at length,
however, it ends by decomposing and leaving behind a granulous residue. Potassium
does not suddenly dissolve it, as it does mucus or albumen, and appears only to hasten
its decomposition by water ; nitric acid and alcohol suddenly coagulate it and render
it white and opaque. Its properties are then very distinct from those of substances
with which some authors have confounded it, for its insolubility in water distinguishes
it from albumen, and its insolubility in potash likewise distinguishes it from mucus,
gelatine, etc. . . . The most simple animals, amoebas, monads, etc., are wholly com-
posed, at least in .appearance, of this living jelly. In the higher Infusoria it is con-
tained in a loose tegument which opens on its surface like a network, and through
which it can pass out in a state of almost perfect isolation. . . . We find sarcode in
eggs, zoophytes, worms and other animals ; but in these it is suscejjtible of receiving
with age a degree of organization more complex than in animals lower in the scale.
. . . Sarcode is without visible organs, and without appearance of cellulosity; but,
however, it is organized, because it throws out divers prolongations, drawing along in
them granules, altern.ately extending and retracting them, .and, in a word, it has life."

The observations of the past fifty years have made little change in Dujardin's
characterization of this substance, but his name has become well nigh forgotten, and
for it lias been substituted the word protoplasm. This new word was first bestowed
upon it by Purkinje in 1839-40. Afterwards the celebrated botanist Hugo von Mohl,
ignorant of the existence of the word, said in 1846 (Bot. Zeitung), " I believe myself

INTRODUCTION. ' Ixv

authorized to give the name of protoplasm to the semi-fluid substance, azotic, made
yellow by iodine, which iij spread throughout the cellular cavity, and wliich furnishes
the material for the primordial utricle and nucleus." Thus a comparative anatomist
and a botanist each independently applied the same name to the living substance com-
mon to both animals and plants.

Dujardin's researches attracted great attention, and ni 1861 Max Schultze did not
hesitate to aflirm the identity of animal cells in general with sarcode. Briicke (1861),
Schultze (1863), and Kiilme (1864), finally demonstrated the identity of living mat-
ter in the two kingdoms, as to its fundamental physical properties : irritability and
contractility.

Since the beginning of the second half of this century (1850-1884), zoological
science has been developed with great rapidity in all directions, but in none more than
in embryology and morphology, v.diile the number of workers lias vastly increased.
Moreover, the general respect and sympathy for biological research, felt by all edu-
cated minds, has encouraged the active workers ; hence the formation and endowment
of new academies and societies, the establishment and suppoi-t of journals of advanced
m -irphology ; the building and rearrangement of museums, and the installation of labor-
atories for original research. Private ex23lorations in all parts of the earth, and the
numerous surveys, especially those of the United States, both state and national, have
fostered and extended zoological knowledge.

Several general treatises on embryology have been published, by Wolff (1759), Von
Baer, Agassiz, Haeckel and Packard, but the last of these treatises, Balfour's Compar-
ative Embryology, is an epoch-making work on development, indicating the third
stage in the history of biological science ; Wolft''s marking the first, and Von Baer's
the second.

The great steps in the discovery of the way animals reproduce and develop were
the discovery of spermatozoa by Leeuwenhoeck in 1677, and that of the mammalian
egg by Degraaf in 1673. A century and a half later Von Baer confirmed the latter,
and showed that all mammals develop from eggs, and then Coste, Valentin, and Jones
showed that these eggs were homologous with those of the lower vertebrates.
The next step was the discovery by Remak, in 1850, of the three germinal layers ;
then Huxley, in 1859, homologized these with the tissues of the coelenterates. The
last steps to be mentioned are investigations of the brothers Hertwig on the meso-
blast and the cceloni, and those of Lang and of Sedgwick on metameric segmentation
and the homology of the blastopore throughout the animal kingdom. While the
future will doubtless pi'oduce many important discoveries, and corrections of existing
errors, it would seem that the leading features of embryology are already established.

The earlier writers on evolution were Lamarck, Geoffrey St. Hilaire, and Goethe.
The literature of evolution, which has characterized the second half of this centui-y,
is the scientific oft'spring of Darwin's Origin of Species, which appeared in 1859, a pre-
liminary essay by Darwin and by Wallace being offered the previous year. It is the
leaven which has leavened the whole lump of modern scientific and philosophical
thought. It was the work of a zoologist, whose studies of systematic and anatomical
zoology as well as geographical distribution converged toward the conception that
species had originated from natural causes. Alfred R. Wallace, also, as the result of
his travels and researches on the Amazon River, and especially in the Malay archipel-
ago, arrived nearly simultaneously at the same conclusion ; his original essay written
at Sarawak in 1855, with others, collected in 1870, are entitled Contributions to the

Ixvi THE ANIMAL KINGDOM.

Theory of Natural Selection, while 11. W. Bates, after spending eight years of re-
search and travel in Brazil, was also led to adopt the theory of natural selection.
Fritz Miiller (Ftir Dnrwin, dated Desterro, Brazil, 1803) and his brother, the late Her-
mann Miiller, in numerous botanieo-entomological tracts and works, as well as Haeckel
in his History of Creation, his Anthropogeny, and other works, and Weissmann's
Studies in the Theory of Descent (1875) are the epoch-making works of this period,
based, as they are, on special studies. Expounders of the doctrines were Huxley
(1859), Herbert Spencer, Haeckel, Asa Gray, and many others. Of the rise of a
modernized Lamarckian school in the United States, of which Hyatt, Cope, Dall,
R^der, and Packard are the sujiporters, mention has already been made. In Germany
this school is represented especially by Semjier.

Witli a knowledge of zoological classification and embryology, naturalists have,
since the publication of Darwin's epoch-making work on the origin of species, published
theories as to the jirobable ancestry and succession of forms, and entered into the con-
struction of genealogical trees, or, in a word, of phylogenies. Haeckel in 1870 first dared
to express diagrammatically liis views as to the phylogeny of anmials in general, his
most authoritative work relating to the ccelenterates, especially the medusDe. Attempts
to trace the genealogy of the insects have been made by Brauer, Packard, Lubbock,
and Mayer ; Hyatt has elaborated the phylogeny of the Ammonites, and Owen, Hitx-
lej', Ivowalevsky, and Marsh the ancestry of certain ungulates, especially of the
horse family, while the phylogenies of the Camelidai', the Carnivora, the Ungulata in
general, and other orders, have been worked out by Cope.

The effect of these studies on paleontology has been marked, and have given a new
direction to the study of the geological succession of animals. The great works of
James Hall, of Barrande, of the Surveys of India, and the explorations in the western
tertiaries by Haydcn, which were published by Meek, Leidy, and others, and the per-
sonal explorations of Marsh and of Cope, as well as those of Gaudry in Euro])e, have re-
vealed numbers of forms connecting the orders of living reptiles, birds, and mannnals,
while the researches on the succession and ancestry of the Ammonites by Hyatt
have opened new fields of research.

In 1864 the Norwegian naturalist, M. Sars, and his son, G. O. Sars, carried on
dredging to the de])th of over 300 fathoms, showing that Forbes (before that time the
most ])rominent writer on marine zoology and the laws of bathymetrical distribution),
was incorrect in inferring that the sea below the depth mentioned was barren of life.
As early as 1850, Michael Sars opposed Forbes' hypothesis, and in 1864 published a list
of 92 different sjiecies discovered at 200-300 fathoms on the coast of Norway, and in
1868 he increased the list to 427 species. As the results of his father's and his own
examinations. Prof. G. O. Sars, as early as 1869, said : " The results of these, my deep-
sea researches, was, however, great and interesting quite beyond all anticipation. . . .
And so far was I from observing any sign of diminished intensity in this animal life at
increased depths, that it seemed, on the contrary, to me as if there was just l)eginning
to appear a rich and in many respects a peculiar deep-sea fauna, of which only a
very incomplete notion had previously existed." The United States Coast Survey,
since 1867, under the inspiration and labors of Agnssiz and Pourtnles, showed that
the bottom of the Floridan channel, below 300-500 fathoms, was packed with life-
forms ; the Swedish Spitzliergen exi^editions also brought u]i deep-sea animals from
2000-3000 fathoms. Meanwhile, the English government sent out the ' Porcujiinc ' and
other vessels, the naturalists of which were Carpenter and Jeffreys, who carried on

INTRODUCTION. Ixvii

extensive deep-sea explorations in tlie North Atlantic, winch were so successful and
full of interest as to stimulate the British government to equip and send out, under
the scientific direction of Wyville Thompson, aided by W. von Suhm, Moseley and
others, the 'Challenger,' which made a voyage around the globe in 1872-76.

The results were full proof of the existence, in all seas throughout the world, of a
fauna unique and extensive, generally known as the abyssal fauna, thus adding a new
world of life, with previously unknown orders of animals, involving new problems in
paleontology and biology, and innneasurably extending our conceptions of the worlil
and its inhabitants and their mutual relations. The voluminous results of this most
important of all the voyages of scientiiic discovery, since that of Columbus, are still
incomplete. Important additions to the facts gathered by the 'Challenger' and pre-
vious explorations, have been made by the Swedish expedition of the 'Josephine,' the
naturalists of which were Smith and Ljungniann, and by the U. S. Commission of Fish
and Fisheries, S. F. Baird, Commissioner, of which A. E. Verrill, in charge of the in-
vertebrates, has from time to time ])ublished important results.

The Austrian, Portuguese, and French governments have sent out similar expedi-
tions, of which, perhaps, the voyage of the 'Talisman,' in 1883, obtained the ricliest
results, A. Milne-Edwards being the naturalist in charge.

Extensive researches with the dredge along the coast of the United States were made
by Agassiz, Desor, and especially Stimpson, from the Bay of Fundy, to Florida, Cuba,
and Yucatan; Packard investigated the shoal-water fauna of Labrador in 1860-64;
while Verrill, Hyatt, Packard, and others have dredged the coast from the Gulf of St.
Lawrence to Cape Hatteras.

The economic value attached to the fisheries led to the formation of the Fisheries
Commissions of Norway, Germany, and the L^nited States ; that of the latter, under
Baird, being especially rich in purely scientih'c results.

The ravages of injurious insects, involving economic questions of vast moment,
have attracted attention from time innnemorial. The destruction of crops and of
forests by these pests led Ratzeburg to devote his life to the subject, resulting in the
preparation of the monumental tomes, richly illustrated and replete with facts, which
have given him an enduring fame. The works of Bouche, Boisduval, and others in
Europe, and of Harris in this country, are also classics.

In America, the state governments established the office of state entomologists,
whose reports, particularly those of Fitch, Walsh, and Riley, are standard works
of reference. The invasion of locusts in the western states and territories led
the national government to establish the U. S. Entomological Commission, consisting
of Riley, Packard, and Thomas, which existed for five years (1877-81).

In 1873 Agassiz estalilished at Penikese, an island in Buzzard's Bay, a seaside labor-
atory for teachers and for students of marine animals. After two years it ceased to
exist. It led to the formation of the Chesajieake Zoological Laboratory of the Johns
Hopkins University, under the direction of Prof. W. K. Brooks, while Mr. A. Agassiz
built a well-appointed private laboratory at Newport. Led by Agassiz's example,
Anton Dohrn established the costly zoological station at Naples, where gather natural-
ists of different countries, whose researches, carried on under such favorable auspices,
have had a manifest influence on morphological studies. Smaller laboratories have
been established by Lacaze Duthiers at Roscoff, Banyul sur Mer in France, and by
Hyatt at Annisquam, in Massachusetts; while during the years 1876-81 a summer
school of biology founded by Packard, was carried on by the Peabody Academy of
Science at Salem, Massachusetts.

Ixviii THE ANIMAL KINGDOM.

Let us now review in a brief manner tlie work done by our countrymen. Ameri-
can zoological science dates only from 1796, when Barton published his memoir On the
Fascination attributed to the Rattlesnake, while his Facts, Observations, and Conjectui-es
on the Generation of the Opossum appeared in 1801. These were simjily memoirs,
but still talented productions and not unworthy to begin the century. Previous to
this, John Bartram published a few zoological tracts in the Philosojjhical Transactions
of the Royal Society of London, the first appearing in 1744.

American systematic zoology may be said to date from the years 1808-14, when
the successive volumes of Wilson's Ornitliology were published, though it should be
remembered that Wilson was born and bred in Scotland. Thus, with the exception
of Bartram's and Barton's works, what we have to say of American zoology (includ-
ing animal physiology, psychology, and embryology) covers only about three quar-
ters of a century. The next work was by Prince Bonaparte, on birds, a volume
supplementary to Wilson's great work, and published in this country in 1825-33.

The first general work by a native-born American was Dr. Richard Harlan's Fauna
Americana, published in 1825. This was succeeded by Dr. John D. Godman's work
on North American mammals, published in three volumes in 1826-28. Bartram,
Barton, and Harlan were born in Philadelpliia and tauglit anatomy there. Godman
was born in Annapolis, and lectured on anatomy in three medical colleges, but not in
Philadelphia. Thomas Say's American Entomology (1824-28) was of a more special
character. On the whole, American zoology took its rise and was fostered chiefly in
Philadelphia by the professors in the medical schools ; and zoology the world over
may be said to have sprung from the study of human anatomy as taught at the ana-
tomical centi-es of Italy, France, England and Germany.

The last half-century of progress in zoology in America may be divided into three
epochs comparable to those enumerated on a preceding page : —

(1.) The epoch of systematic zoology, during which a few ]ihysiological essays ap-
peared. To this division of zoology a most decided impulse was given by tlie
Smithsonian Institution, which went into active operation in 1847, while the study of
the fossil forms (paleontology) was greatly accelerated by the influence of national
and esjiecially state surveys.

(2.) The epoch of morphological and embryological zoology. This period is due
to the arrival of Louis Agassiz in this country, in 1846, resulting in his lectures on
comparative embryology and the foundation of the Museum of Comparative Zoology,
whei-e American students, who were attracted by the fame of Agassiz, were instruct-
ed in the methods of Cuvier, Von Baer, Dollinger, and Agassiz himself, and zoology
was studied from the side of histology and embryology, wliile paleontology was
wedded to the study of living animals.

(3.) The epoch of evolution, or the study of the genetic relationship of animals,
based on their mutual relations and their physical environment. This period dates
from the publication of Darwin's Origin of Species, in 1859.

Turning, now, to the first epoch, — that in which American systematic zoology
took its rise, — we find that work was done which must necessarily precede more
important studies on the embryology, geographical distribution, mutual relations, and
psychology of animals ; thus exerting a marked influence on the classification of animals,
which nowadays is equivalent to tracing their genetic relationships ; for the time is
past when the animal world should be regarded as comjirised within separate sub-
kingdoms, between which there is no morphological or genetic connection.

INTRODUCTION. Ixix

The systematic works are so well known, and our space so limitetl, that we shall
merely enumerate the names of our chief zoological authors. In the study of mam-
mals the works of Audubon and his predecessors, already named, and of Thomas Jef-
ferson, T. Say, J. Baehmann, G. Oi-d, S. F. Baird, T. Gill, Harrison Allen, J. A. Allen,
E. D. Cope, Elliott Coues, J. Y. Seammon, B. G. Wilder, C. H. Merriam, and W. S.
Barnard, should he mentioned, with the paleontological essays of R. Harlan, J. C.
Warren, J. Leidy, E. D. Cojie, and O. C. Marsh, together with Godman's Rambles of
a Naturalist, L. H. Moi'gan's work on the beaver, Merriam's on the Mammals of the
Adirondacks, and physiological essays by J. Wyman, S. Weir Mitchell, J. C. Dalton,
and others.

The ornithological works of Wilson, Bonaparte, Audubon, Nuttall, Baird, Cassin,
and Coues, the more recent great work of Baird, Brewer, and Ridgway, Cones' Key
to the North American Birds, Birds of the Northwest, and Birds of the Colorado
Valley, and the many descri]jtive and biological papers of other authors, such as T.
M. Brewer, Ord, J. P. Giraud, J. K. Townsend, A. L. Heerman, G. N. Lawrence, D.
G. Elliott, H. W. Gambel, J. Xanthus, L. Stejneger, H. W. Henshaw, H. Byrant, S.
Cabot, T. M. Tri]ipe, .J. A. Allen, C. H. Merriam, W. H. Brewster, and others, with
the papers on distribution by Baird, A. E. Verrill, J. A. Allen, and R. Ridgway,
together with those on fossil birds by Marsh, are all worthy of comparison with the
best European works and papers.

The reptiles and amphibians have been described by Harlan, J. E. Holbrook, T.
Say, J. Green, Baird, C. Girard, S. Garman, E. Hallowell, L. R. Gibbes, C. A. Lesueur,
J. L. Le Conte, L. Agassiz, and Cope, and an entire assemblage of forms in the west-
ern cretaceous and tertiary formations has been discovered by Leidy, Blarsh, and
Cope. The anatomy of the nervous system of Rana pipiens, by Jeffries Wyman, is
a classic, as are the researches of S. Weir Mitchell upon the venom of the rattlesnake,
and the researches on the anatomy and physiology of respiration in the Chelonia, by
S. Weir Mitchell and G. R. Morehouse.

The fishes of North America have been worked up by S. L. Mitchell, Lesueur, C.
S. Rafinesque, D. H. Storer, .J. E. Dekay, Holbrook, Agassiz, Girard, J. P. Kirtland, J.
C. Brevoort, Wyman, Baird, Gill, Cope, W. O. Ayres, F. W. Putnam, T. G. Tell-
kampf, D. S. Jordan, H. C. Yarrow, C. C. Abbott,' G. B. Goode, R. Bliss, S. W. Gar-
man, W. N. Lockington, C. H. Gilbert, J. H. Swaim, and others ; while the fossil
forms have been described by J. H. and W. C. Redfield, Leidy, R. W. Gibbes, J. S.
Newberry, Cope, O. St. John, E. W. Claypole, and others, and several species of
Tunicata have been described by C. A. Lesueur, Tellkampf, Louis and A. Agassiz,
Verrill, and Packard.

In entomology the writings of Say, the two Le Contes, F. E. Melsheimer, N.
Hentz, T. W. Harris, S. S. Haldeman, R. von Osten Sacken, B. Clemens, J. D. Dana,
G. H. Horn, S. H. Scudder, P. R. Fhler, H. Hagen, B. D.jWalsh, A. S. Packard, A. R.
Grote, W. II. Edwards, Henry Edwards, C. H.Fernald, H. C. Wood, A. Fitch, C. V.
Riley, E. Norton, J. H. Emorton, C. Thomas, S. W. Williston, R. H. Stretch, H.
Strecker, J. B. Smith, J. H. Comstock, L. O. Howard, E. T. Cresson, and others, are in
most cases quite voluminous, though mostly descriptive, wliile the fossil forms have
been described by Scudder, Dana, Meek and Wortlien, S. I. Smith, and O. Harger.
Their anatomy and histology has been studied ))y Leidy, Scudder, Packard, G. Dim-
mock, E. Burgess, C. S. Minot, and G. Macloskie.

The great work of Dana on the Crustacea of the L^nited States Exploring Expe-

Ixx THE ANIMAL KINGDOM.

ditioii placed him next to Milue-Edwards at the head of Hving authors in tliis depart-
ment, and his essay on their geograpliical distribution is the starting-point for all such
inquiries. The Noith American species have been described by Say, W. Stimpson,
J. W. Randall, L. K. Gibbes, S. I. Smith, Ilagen, W. N. Lockington, E. A. Birge,
C. L. Herrick, W. Faxon, Packard, O. Harger, and J. S. Kingsley, and the fossil forms
by Green, Hall, Billings, Stimpson, Packard, C. E. Beecher, Clarke, C. D. Walcott,
and others.

The intestinal and higher worms have been worked up by D. Weinland, Girard,
Leidy, Wyraan, Verrill, Stimpson, Minot, Webster, Benedict, Sager, Whitman,
and Wright ; and of the aberrant classes some of the Polyzoa have been carefully
studied by A. Hyatt, and the Brachiopoda by E. S. Morse and W. H. Dall.

The molluscs of North America have been elaborated by Say, Gould, Lesueur,
Rafinesque, Haldeman, I. Lea, T. A. Conrad, Anthony, C. B. Adams, Stimpson, the
two Binneys, J. W. Mighels, J. P. Couthouy, Gabb, A. Agassiz, T. Bland, T. Prime,
Morse, J. Lewis, Dall, Tryon, Verrill, R. E. C. Stearns, Sanderson Smith, and others.
The fossil Mollusca of entire formations have been described by Hall, Billings (of
Canada), F. B. Meek, C. A. White, F. S. Holmes, O. St. John, C. F. Hartt, R. Rath-
bun, O. A. Derby, Whitfield, N. S. Shaler, Whiteaves (of Canada), and other paleon-
tologists ; and the quaternary species studied by Holmes, Dawson, Stimpson, Packard,
Verrill, Matthews, and others. Their anatomy has been studied by Leidy, Wyman,
Morse, Dall, W. K. Brooks, and H. L. Osborn ; while B. Sharp has studied their
visual organs.

The cfflenterates and echinoderins have been carefully elaborated liy Louis and A.
Agassiz, and by Say, Stimpson, E. Desor, Ayres, Macrady, H. J. Clark, T. Lyman,
Pourtales, Verrill, W. K. Brooks, S. F. Clarke, E. B. Wilson, J. S. Kingsley, J. W.
Fewkes, H. W. Conn, and H. G. Beyer; while Dana's elaborate report on the Zoo-
phytes of the United States Exploring Ex]iedition took the highest rank among syste-
matic works. Numerous fossil forms have been brought to light by Hall, Billings,
Meek, Shumard, Springer, White, Wachsmuth, Whitfield, W^ H. Niles, O. A. Derby,
and other paheontulogists, and the distribution of the recent forms on both sides of
the continent has been studied by Verrill and A. Agassiz.

The sponges have been chiefly studied by Clark, Hyatt, Potts, and 3Iills ; and the
Protozoa by Leidy, J. W. Bailey, H. J. Clark, A. C. Stokes, J. A. Ryder, and D. S.
Kellicott.

We may congratulate ourselves on the high position of our paleontologists, in the
scientific world. The labors of James Hall, Meek, Billings, Dawson (of Montreal ;
we include Canadian students), and others, have revealed whole platfcnnis of life in
the palaeozoic rocks ; while the researches of Leidy, Cope, Marsh, and W. B. Scott and
H. F. Osborne, in the tertiary, cretaceous, and Permian beds of New Jersey and the
west, and of Denne, Hitchcock, Leidy, Wyman, Newberry, Emmons, and Cojie, in
triassic and carboniferous strata, have been productive of valuable residts.

The discovery of the fossil bird-like reptiles of New Jersey, by Leidy and Co])e ;
of birds with teeth, and pterodactyls without teeth ; of lennu'-likc monkeys, by
Marsh ; of camels, by Cope ; and the discovery by Leidy, Marsh, and Cope, of con-
necting links between living ruminants and liog-like forms, and between elephants
and tapirs; together with the genealogy of the horse, and tlie increase in the size of the
brain of living forms over their tertiary ancestors, as elaborated liy iNIarsh, all ]iresent
amass of new facts bearing on the evt)lation of life on the American continent, and

INTRODUCTION. Ixxi

the general doctrine of evolution. The labors of W. B. Scott and H. F. Osborne
should also be mentioned here.

The epoch of embryology, or the developmental study of animals, was inaugurated
by Agassiz in 1846. In tlie publication of his Contributions to the Natural History
of the United States, mainly devoted to the developmental history of the coelenter-
ates and turtles, Agassiz was assisted l)y H. J. Clark. Macrady, another of Agassiz's
students, published some papers of importance on the Acalephs and their mode of
development. Desor and Girard wrote on the embryology of worms. Memoirs of a
high order of merit followed from the pen and pencil of Mr. Alexander Agassiz. His
embryology of the echinoderms appeared between 1864 and 1874; the memoir on the
alternation of generations of the worm, Autoli/tus, appeared in 18G2 ; his pajier on
the early stages of annelids in 1866 ; his remarkable memoir on the transformation of
Tornaria into JBalanoglossus was jjublished in 1873 ; and his elaborate embryology
of the Ctenophores in 1874. In 1864, Jeffries Wyman, at the time of his death the
leading American comparative anatomist and physiologist, ]3ublished a memoir on the
development of the skate. Studies on the development of worms have been made by
J. W. Fewkes and E. B. Wilson, while J. A. Ryder, A. Agassiz, C. O. Whitman, H.
J. Rice, J. S. Kingsley, and H. W. Conn, have worked on the embryology of fishes,
That of the Amphibia has been elaljorated by S. F. Clarke, W. B. Scott, and H.
F. Osborn, and their transformations by Mary Hinckley. The beautiful memoir of
Hyatt on the embryology of Ammonites was a difficult research, while the papers of
Morse on the early stages of the brachiopod, TerebraUdina, published in 1869-73,
led him, by embryological as well as anatomical evidence, to transfer the brachio-
pods from the molluscs to the vicinity of the annelidan worms. Morse and W. K.
Brooks have also examined the development of Lingula. The studies of Morse on
the carpus and tarsus of embryo birds should also be mentioned. In 1870, 1872, and
1880, Packard published memoirs on the development of Limulus, and was the first to
point out the affinities of its young to certain young trilobites ; and he has also published
papers on the embryology of the hexa|)odous insects. Of a high order of merit are
Howard Ayres' elaborate memoir on the development of the CEcanthus niveus, or tree
cricket, with its egg parasite (1884), and William Patten's valuable essay on the
embryology of the Phryganeidas (1884). S. I. Smith, W. K. Brooks, W. Faxon, E.
A. Blrge, and E. B. Wilson have traced the metamorphoses of certain Crustacea.
Several entomologists, as Harris, L. Agassiz, Fitch, Riley, Scudder, Packard, Le Baron,
Hagen, Cabot, Walsh, Saunders, W. H. Edwards, Henry Edwards, S. A. Forbes, J.
A. Lintner, Otto Lugger, and others, have studied the metamorphoses of insects, while
the drawings in illustration of Abbot and Smith's Natural History of the Rarer
Insects of Georgia were made by Abbot, who li\'ed sever.al years in Georgia. In
1874 Emerton described the emljryology of the spider, Pholciis, and in 1876 an impor-
tant memoir by W. K. Brooks, on the anomalous mode of development of Salpa, a
tunicate, appeared. J. S. Kingsley has described the metamorphoses of the ascidian,
Molgula. The embryology of the molluscs, especially of the oyster, has been worked
out by W. K. Brooks and .1. A. Ryder, while E. B. Wilson has treated that of Benilla.
Mention should also be made of the papers by J. W. Fewkes and S. F. Clarke on the
development of coelenterates. In the department of embryology, great activity was
shown by American students when scarcely anything was being done in England or
France, and the United States were for twenty-five years (1850-1875) only second
in embryological studies to German)', the mother of developmental zoology. More

Ixxii THE ANIMAL KINGDOM.

recently England, through the labors of Balfour and his pupils, has advanced to a posi-
tion far ahead of the United States.

Of anthropological authors, we have room only to speak of Morton, Davis, E.
G. Squier, Pickering, L. H. Morgan, Agassiz, Nott and Gliddon, Wyman, J. D. Whit-
ney, Foster, Jones, Abbott, Gatschek, Dorsey, Bessels, Carr, Berendt, Leidy, Baird, Dall,
Powell, Putnam, C. A. White, Ran, Gillman, Meigs, Jackson, Barber, C. Thomas, and
a number of collectors and students now in the field, chiefly of aboriginal archeology.

The third, or evolutional epoch, produced an original and distinctively American
school of evolutionists. Hyatt's memoir On the Parallelism between the Different
Stages of Life in the Individual, and those in the Entire Group of the Molluscous
Order Tetrabranchiata, was published in 1867, and several papers, extending his
views to other groups of Ammonites and molluscs, have appeared since then. Cope's
Origin of Genera was published in 1868, and his pajjer On the Method of Creation
of Organic Types, in 1871. As Cope observes, the law of natural selection "lias
been epitomized by Spencer as the ' survival of the fittest.' This neat expression, no
doubt, covers the case ; but it leaves the origin of the fittest entirely untouched,"
an<l he accordingly seeks for the causes of its origin. Here also should be men-
tioned the writings of Baird, Allen, and Ridgway, on the laws of geographical
distribution and climatic variation in mammals and birds, which have revolutionized
our nomenclature in these classes, and bear directly on the evolution hypothesis.
S]>ecial attempts to ascertain the probable ancestry of American mammals have been
made by Cope, Marsh, and Gill ; of cephalo])od molluscs by Hyatt ; of insects by
Packard ; and of brachiopods by Morse. Contributions to the doctrine of natural
selection have been made by Dr. W. C. Wells, Rafinesque, Haldeman, Walsh, Riley,
Morse, Brooks, and others. The papers by J. A. Ryder on mechanical evolution, and
by Hyatt on the influence of gravitation on the animal organism, deserve especial
mention, as do Whitman's on the theory of concrescence.

In conclusion we may close this historical sketch witli some pertinent remarks of
Galton in his work on Hereditary Genius : —

" The fact of a person's name being associated with some one striking scientific
discovery helps enormously, but often unduly, to prolong his reputation to after-ages.
It is notorious that the same discovery is frequently made simultaneously and quite
independently by different persons. Thus, to speak of oidy a few cases in late years,
the discoveries of pliotography, of electric telegraphy, and of the planet Neptune
through theoretical calculations, have all their rival claimants. It would seem that
discoveries are usually made when the time is ripe for them — that is to say, when the
ideas from which they naturally flow are fermenting in the minds of many men.
When apples are ripe, a trifling event suffices to decide which of them shall first drop
off its stalk; so a small accident will often determine the scientific man who shall first
make and publish a new discovery. There are many persons who have contributed
vast nnmbei's of original memoirs, all of them of some, many of great, liut none of
extraordinary importance. These men have the cap.acity of making a striking dis-
covery, though they had not the luck to do so. Their work is valuable and I'emains,
but the worker is forgotten. Nay, some eminently scientific men have shown their
original jjowers by little more than a continuous flow of helpful suggestions and
criticisms, which were individually of too little importance to be remembered in the
history of science, but which in their aggregate formed a not.able aid toward its
progress." A. S. Packard.

LOWER INVERTEBRATES.

Branch L — PROTOZOA.

In the pages of the Introduction we have a definition of a cell, with a brief account
of the part it plays in the structure of animals, and now in the Protozoa we are to
study the manifestations of cell life in their simplest forms ; for these animals during
theh- whole existence consist each of but a single cell ; yet, simple as this structure
would seem to be, we find manifestations of almost all vital phenomena exhibited by
these forms. Every member of the branch has the power of motion, of assimilating
food, and of reproducing its kind, all of these functions being performed by the single
cell.

In the Cuvierian system of classification no place was accorded to this group, for
they were either regarded as embryonic forms, or, as in the case of the Foraminifera,
they were transferred bodily to some of the four great di^'isions into which the animal
kingdom was divided. Though the Protozoa have been studied for over two hundred
years, it was not until 1845 that they were first considered as unicellular forms, and for
a long time after that date the most prominent naturalists refused to accept the con-
clusions of the illustrious von Siebold. Ehrenberg, who studied these forms very
thoroughly, and in 1838 published a large and extensively illustrated work upon them,
describes with great detail nervous, digestive, motory, reproductive and sensory sys-
tems in these really simple organisms, all of which have since been shown to have no
actual existence. These irdstakes, great as they now appear, arose very naturally, for
at the time at which Ehrenberg wi-ote, Schwann had not made known his studies upon
cells ; and highly preposterous at that day would seem the idea that an animal could
exist without definite organs to perform the functions of animal life. Were space at
our disposal, it would prove an interesting chapter to review the history of the disputes
regarding the character of these forms, the rash and dogmatic assertions of prominent
naturalists who believed that there could be only the four great di^^sions of the animal
kingdom which the great Cuvier had proposed, and, on the other hand, the patient
observations and the guarded statements of their opponents. Time, however, served to
clear up the doubts surrounding these minute forms, and to-day not a naturalist lives
who does not in some way accept the group.

The Protozoa are mostly microscopic animals consisting of but a single cell, or, in
a few cases, apparently of an association of cells, without, however, any differentiation
into tissues. These few apparent exceptions will be considered more at length further
on. In some of the Protozoa the cell is provided with a nucleus and various other
differentiations of the protoplasm ; in others no such structures have as yet been dis-
covered, the animal, so far as our knowledge enables us to say, being but a cytode, a

VOL. I. — 1

2 LOWER INVERTEBRATES.

mass of protojalasm capable of talcing food and reproducing its kind. Concerning these
latter our knowledge is not absolute, and further observation may show that in these
a nucleus really exists, a result rendered more probable by the fact that in the Forami-
nifera, in which the existence of a nucleus was long denied, that specialization of the
protoplasm has recently been discovered. Another feature which frequently occurs in
the Protozoa is the contractile vacuole. This is as yet a problematic arrangement, the
function of which cannot be said to be decided. There appears in the body a clear
vesicle which, sometimes si^herical, sometimes irregular and ramified, slowly increases
in size, and then suddenly contracts, leaving no trace, and then gradually appears again,
only to repeat the operation. It is thought that in some cases these contractile vacu-
oles communicate with the exterior, but this has not been proved. In short, there
remains a fine field for investigation in the structure and functions of these problem-
atical organs, which ^^dll be described more in detail in the succeeding pages.

Food is taken by the Protozoa into the interior of the body, the digestible portions
assimilated, and the portions of no use to the organism afterward rejected. In the
lower forms all parts of the body seem to be equally adapted for the capture and
engulf ment of food, the Protozoan simply crawling around the object; while in the
higher there is a distinct portion of the cell set ajjar*^ for the introsusception of nutri-
ment. The character of nourishment also varies, some forms living on vegetable pro-
ductions alone, while others absorb any organic bodies, animal or plant, often devouring
forms, rotifers, worms or Crustacea, far higher in the scale than themselves. In tlie
higher Protozoa the food is either brought to the part of the body set aside for the
reception of food by currents of water created by rapidly moving cilia, while in others
the animals which are eaten are in some unexplained manner benumbed by the Proto-
zoan and then devoured. When taken into the body the aliment forms a mass slowly
circulating through the protoplasm and is known as a food vacuole.

Reproduction is accomplished in several distinct ways ; by fission, by budding, by
encystment, and the subsequent formation of young, in which the act of conjugation
frecjuently ])lays a j)art not yet vinderstood. Two and sometimes more individuals
unite and form a single mass, and then either separate, or the whole becomes encysted ;
but whether this is to be regarded as a true sexual act, or as an obscure something not
clearly defined by the term applied to it of " rejuvenescence," has not been settled.

Four well-marked groujis of Protozoa occur ; Monera, Gregarinida, Rhizopoda, and
Infusoria. The great German naturalist Hteckel has proposed a third division, Pro-
tista, of organized beings to contain forms which cannot be certainly classed with either
the animal or the vegetable kingdoms, and here would come the group IMonera, together
with other clearly closely alUed groups which, by common consent rather than by
definite character, are usually regarded as belonging to the vegetable kingdom. But
though hard and fast lines do not exist in nature, we are compelled to create boun-
daries which are frequently as arbitrary as any to be found in geographies, and for the
pur|)oses of this series we prefer to consider the Monera as belonging to the animal
kingdom, and to ignore the claims of the Protista.

Class I.— MOI^TERA.

The Monera, the lowest group of the Protozoa, may be briefly described, following
partly the language of Hseckel, as follows : —

MONERA.

Organisms without organs. The entire body consists of nothing more than a bit
of plasma or primitive jelly, an albumenoicl compound not differentiated into j)roto-
plasm and nucleus. Every Moner is therefore a cytode but not a cell. Their form is
indefinite, with lobes or pseudopodia projecting from any part, by means of which they
move. They multiply by division, budding, or by the formation of spores, as will be
described further on. They live mostly in water. The manner in which the Monera
envelop and flow around their food shows the absence of a definite limiting membrane
or cell-wall, and also the extreme simplicity and homogeneous character of their bodj"-
substance ; since any portion of it surrounding a particle of food causes digestion and
assimilation to take place. This method of securing food will be more fully described
when treating of the Amceba. The reproductive processes are rather moi'e complex
than would be anticipated
among such low forms of life.
The simj)lest method of propa-
gation is by division of the or-
ganism into two parts by a
construction across the middle,
forming two animals precisely
like the j)arent form.

The Protomyxa auranti-
aca represented in Fig. 1, is a
typical Moner. It is shown at
(/■) in its active, creeping con-
dition, the jjseudopodia stream-
ing outward in all directions
with clear spaces or vacuoles
and food particles in the in-
terior. The food is entangled
in the reticulate pseudopodia
and gradually drawn into the
body, where a temporary stom-
ach is formed by the surround-
ing protoplasm. After the di-
gestible portions are absorbed
the rest is cast off from any
part of the surface. This
Moner multiplies by the foi-
mation of swimming spores in
this manner : The pseudopodia
are all retracted and the Moner
becomes spherical (a). It then
becomes encysted by the for-
mation of a thick outer mem-
brane, meanwhile changing to an orange-red color. The cyst ripens by the sub-
division of the contents (6), and finally the enclosing membrane ruptures (c), and
the contents escape as bright red, active swarm-spores, which swim about by the aid
of the delicate, lashing flagella or threadUke extensions of the protoplasmic body.
These changes are illustrated in the figure a, h, c, and d, being the successive stages

^^^^4

Fig. 1.

■ Protomyxa auriantlaca ; a. encysted ; h. division of proto-
plasm ; c. cyst bursting, giving rise to the spores, d. e., from
which, by coalescence, the feeding Plasmodium,/., is formed.
Greatly enlarged.

4 LOWER INVERTEBRATES.

from cyst to swarm-spores, and e being the first stage of reversion from swarm-spores
to the mature form.

The swarm-spores, to which the name plastidiiles has been given, are masses of
apparently structureless protoplasm, manifesting life in its simplest conceivable form.

Class II. — RHIZOPODA.

No definite boundary can be drawn between the Monera and the Rhizopoda, and it
is doubtful if the simple Protomyxa just described as a typical Moner, does not justly
deserve to rank in this class. In a general way it may be said that the Rhizopods are
distinguished from the Moners by having a more or less well-defined outer layer of sar-
code and a nucleus, although the latter is not always to be observed.

The Rhizopoda have been divided by Dr. William B. Carpenter into three groups,
distinguished by the character of their sarcode or pseudopodia ; the Lobosa, in which
the pseudopodia are lobose or finger-like, as shown in the illustration of Amoeba pi'o-
teus, Fig. 2 ; the Radiolaria, in which the sarcode extends outward in rays more or
less constiint in form and position, as in Actinophrys, Actinosphcerium or Clath-
rulina., Fig. 10, among fresh-water forms, and liotalia. Fig. 15, among the marine
forms; the Reticularia, in which the sarcode extends in irregular, soft anastomosing
branches, which coalesce whenever they come together, as well illustrated in Gromia,
Fig. 11. Dr. Carpenter groups all the Rhizopods under these three heads, as fol-
lows : —

LOBOSA.

ADIOLARIA.

Keticulakia.

Amoebina.

Actinopliryna.

Gromida.

Acantlioraetrina.

Foraminifera,

Polyeystina.

Thalassicollina.

This arrangement is not founded upon any physiological or morphological distinc-
tions, and it can only be regarded as provisional. The different groups merge into one
another so that the character of the pseudopodia alone is a very unsatisfactory guide,
esjjecially in distinguishing between the lobose and the reticularian forms. The
Radiolaria are the most complex in structure of all Rhizopods ; the marine foi-ms pro-
duce silicious skeletons of great variety and beauty. The Reticularia include the
marine Rhizopods with calcareous shells, often quite complex in structure ; some of
them grow to a comparatively large size. The immense beds of chalk of the Old World
are largely composed of the shells of Foraminifera, and the Eozoon canadense, claimed
by some to be the oldest form of animal life known to the geologist, if really an aui-
mal, also belongs to this group.

Our fresh-water Rhizopods have been treated very fully by Prof. Josejih Leidy in
his "Fresh-water Rhizopods of North America." He has diN-ided them into the Proto-
plasta, from p^^'otos, first and plasso, a form or mould ; and the Seliozoa, from helios,
the sun, and zoon, animal. The Protoplasta are divided into the Protoplasta lobosa,
which corresponds to the Lobosa of Carpenter, and Protoplasta filosa, which are
included in the Reticularia of Carpenter. The Heliozoa, which live in fresh water,
are closely allied to the marine Radiolaria, but their precise relations are not yet
understood.

RHIZOPODA. 5

We may then divide the whole of the Rhizopoda into four orders : I. Lobosa ;
II. Radiolaria ; III. Heliozoa ; IV. Reticularia.

Order I.— LOBOSA.

The Lobosa are characterized by blunt, digitate extensions {pseudopodia) of the
soft body-mass, by means of which the animals move about and capture their food.
The animals may be unprotected by a covering of any kind, or they may have shells of
chitinous material or of cemented grains of sand or debris of any kind. The soft body
is similar in structure in all cases, and the naked form known as the Amceba affords
the best subject for studying this group of animals.

The Amoeba proteus is represented in Fig. 2, and may be taken as a type of all
the lobose protoplasts. It consists of an outer portion of protoplasm, termed the
ectosarc, rather more consistent and clearer than the rest, but continuous with it, and
an inner, more fluid portion, containing granules and known as the endosarc. There is
no permanent differentiation between the endosarc and the ectosarc, for as the animal
moves, or takes in particles
of food, portions of the
ectosarc may become in-
folded, and they then im-
mediately become conflu-
ent with the endosarc.
Probably the only differ-
ence between the two
portions of the proto-
])lasm is that caused by
contact with the surround-
ing watei', which seems to
partiall}^ coagulate the ex-
ternal portion. The Am-
oeba moves by extending a
portion of the clear ecto-
sarc in any direction, when
the granules of the endosarc will be seen to follow, as though flowing into an empty sjjace.
The form of the Amoeba is therefore constantly changing, — pseudopodia are projected
in any direction, singly or several at one time, while the granules are in constant
motion.

The granules do not seem to be essential constituents of the protoplasm. They are
of all sizes, from almost immeasurably minute particles up to comparatively large ones.
They seem to be inert particles, many of them doubtless being the remains of sub-
stances collected as food, but frequently there are seen globules of oil and spherical
green corpuscles which are supposed to contain chlorophyl.

Within the endosarc a nucleus is often readily observed. A nucleus is regarded as
an essential element in the Rhizopod structure. It appears as a spherical or discoid,
colorless, clear, or granular corpuscle, within which may or may not be seen a still
smaller body known as the nucleolus.

jfi^fe^s^:^'ji|jj

Fig. 2. — Amoeba proteus, greatly enlarged.

6 LOWER INVERTEBRATES.

There is also a curious jjulsating vesicle witliin the endosarc, but often it encroaches
upon the ectosarc so much as to seem a part of the latter. This vesicle originates as a
clear spot in the ])rotoplasm, which slowly enlarges until it reaches a considerable size,
when it suddenly collapses. There is a regularity in this occurrence which may be
observed to be repeated several times in a minute. The function of the contractile
vacuole, which is very common among the Infusoria, has not yet been fully determined.
It is supjjosed that it subserves the respiratory process, but some authors regard it as
subserving an excretory purpose. Whether the fluid of the vacuole is forced out into
the surrounding water as the vesicle closes has not been satisfactorily demonstrated,
although there is strong evidence pointing to that conclusion.

Food is taken into the body of the Amceba through any part of the surface. A
portion of the ectosarc extends around the prey, enclosing it along with some of the
water, which then sinks down into the endosarc, where it forms a so-called food-ball ;
such food-balls may become quite numerous in a single animal. Ehrenberg, supposing
them to be permanent stomachs, gave the name Polygastrica to those Protozoa in which
he observed them. Any portion of the Amoeba's body will serve the purpose of a tem-
porary stomacli, in which food may be digested and assimilated. The indigestible por-
tions are ejected at any part of the surface, but usually at the postei-ior part, near the
contractile vesicle. The food of the Amoeba is usually of a vegetable nature. The deli-
cate filamentous desmids seem to be a favorite food, and diatom remains are often found

in the Amceba in great abundance. In assimilating
the nutriment of a filamentous desmid, the Amceba
passes along the filament, enveloping cell after cell,
seemingly passing the plant directly through its body,
absorbing the contents and rejecting the indigestible
jwrtions.

The Amoebae propagate by division and perhaps
by a process of conjugation ; at least an appearance
of conjugation has been observed in a few cases.
When the circumstances of life are unfavorable, the
Amcebse may become encysted, by which means they

,, — .^:=^a~iia»«- are able to withstand great changes of external con-

^ggl • -- •■ —

, ditions. When about to become encysted, the re-

¥iG. 3.— JJijIliu/ui uirculata. Enlarged. _ ...

mains of food and particles of indigestible matter are
rejected, and the animal assumes a spherical shape precisely like Protomyxa, Fig. 1, a,
soon becoming surrounded by a more or less thick membrane composed of several layers.
In this protected condition the Amceba may rest a long time, and then, by rupturing its
envelope it may again come forth apparently unchanged. But in some cases a change
takes place within the capsule which results in the formation of a large number of
sjiherical germs or spores, each of which iirobably escapes and grows into a new form,
as in the case of Protomyxa, already described.

A large number of the Lobose protoplasts are provided with shells, many of them
of regular and beautiful form. Of these, Difflugla, Fig. 3, may be taken as a rejire-
sentative genus. The shell of this Rhizopod is spherical or oval, composed of grains
of sand mingled with frustules of diatoms, spicules, etc., cemented together. The
sarcode-body almost fills the shell, and is attached to it by protoplasmic threads passing
to the fundus and sides. The shell is open at one end, where the blunt cylindrical
pseudopodia are projected either for the prehension of food or as organs of locomotion.

RHIZOPODA. 7

In size it may vary from .036 mm. to .260 mm. in lengtli. The nucleus and contractile
vesicle are conspicuous in the posterior portion. In all the shelled forms the food is
taken in at the mouth of the shell, and the debris is ejected at the base of the pseudo-
podia.

Oeder II. — RADIOLARIA.

When Prof. Huxley was engaged in studying the fauna of the sea on board H. M. S.
"Rattlesnake," about thirty years ago (1851), he found floating upon the seas, whetlier
tropical or extra-tropical, some peculiar gelatmous bodies to which he gave the name
ThcdassicoUa., signifying sea-jelly. These were among the most common objects from
the tow-net, and their extreme simplicity of structure made it very difficult to classify
them in the animal kingdom. Imagine a colorless, transparent gelatinous mass, spheri-
cal, elliptical, or elongated in form or contracted like an hour-glass in one or more
places, varying in size from a mere spec up to
an inch in length, without contractility or power
of motion, but floating passively upon the
water : such is Thalassicolla, Fig. 4.

Two species were described by Prof. Hux-
ley in his account of these organisms. One
of them, T. punctata, is characterized by an
appearance of dots scattered about near the
internal surface of the thick, gelatinous crust
which may surround either a single large
cavity or a number of clear spaces closely
aggregated. The appearance of dots is pro-
duced by nucleated cells, which are imbedded
in, and held together by, the gelatinous crust.
The cells are about ^J^g- or jtJjj of an inch in
diameter, and are covered with a thin mem-
brane. Surrounding the cells or diffused through the connecting substance are minute
bright-yellow corpuscles. The cells may also be enclosed within a framework of crystals
or spicules resembling the spicules of a sponge.

T. nucleata is a spherical mass, characterized by a blackish central portion, around
which is a zone of vacuoles or clear spaces with yellow cells and dark granules, which
is in turn surrounded by the outer, clear, gelatinous substance. The dark central por-
tion is a vesicle Avith granular contents and a firm, colored membrane. P"'roni the dark
centre delicate branching fibrils radiate and anastomose through the zone of vacuoles,
extending almost to the periphery of the sphere.

Thalassicolla may be regarded as a type of the Radiolarian structure. The Radio-
laria are characterized by having a central nucleated portion surrounded by an outer
peripheral mass, from which it is separated by a porous, more or less resisting mem-
brane known as the capsule. Both the mass within the capsule and the sareode with-
out consist of very soft and contractile protoplasm, in which are imbedded colored
globules, vacuoles, and perhaps other structures. JNIost Radiolaria have a skeletal frame-
work of silicious spicules, or beautifully-designed structures, which may be found either
within or without the capsule. The silicious framework of these minute organisms,

Fig. 4. — Thalassicolla moncm. Greatly enlarged.

8 LOWER INVERTEBRATES.

when properly cleaned and prepared for exhibition, afford some of the most beautiful
objects for examination with a microscope.

The Polycystina especially, which have an external skeleton of clear, glassy sUica,
are to be found in every collection of microscopic objects, and there are few specimens
that attract more imiversal admiration for beauty and regularity of form.

Before describing some of tlie more important representatives of this group, a few
words should be said concerning their general characteristics. The single animals or
zooids vary in size from about ^^jj to gJg- of an inch, or even more, in diameter. They
are usually spherical, but they may be cylindrical, discoidal, or of other shapes. The
sarcode within and without the capsule is continuous through the pores of the chitLnous
membrane which surrounds it. In Thalassicolla the capsule is very small compared
to the size of the animal, but usually, especially in the solitary forms, the capsule is
relatively very large, sometimes having only an exceedingly thin layer of extra capsular
sarcode .about it. The tendency of such simple forms of life is to live in colonies like
Thalassicolla punctata, in which the capsules and the investing sarcode have already
been described as cells imbedded in the gelatinous connecting mass. The capsules
vary in size from 1 mm. down to .025 mm.

The sarcode contains vesicles or alveoli, which may be found both within and with-
out the capsule ; but no regularly contracting vesicle, such as is found in the Heliozoa,
has been observed.

Within the capsule are found peculiar structures which have been termed nuclei,
and -which are supposed to be true nuclei of the capsule. These are of two kuids, —
simple and complex. The simple nuclei measure from .008 mm. to .015 mm. in diame-
ter. Tliey are perfectly homogeneous in appearance, and may exist in great numbers
in a single capsule, almost filling it in fact, or they may be few, or even quite absent
when a complex nucleus is present. They liave no investing membrane. The complex
nucleus is a multi-globular vesicle with a membranous covering snnilar to that of the
capsule itself, but more delicate. It is possible that the simple nuclei are developed
witliin it. The complex nucleus is also designated as the "nuclear vesicle." It is
characteristic of certain forms of Radiolaria.

The sarcode of the capsule may be colorless, or it may be distinctly colored, red,
brown, and yellow being the usual colors. Examination with high powers of the micro-
sco]3e shows the coloring matter in the form of minute vesicles. There are also found
in the sarcode globules of oil or fatty matters, and sometimes concretions, crystals, .and
other structures that may be nothing but remains of food. The external sarcode is not
protected by any definite enveloping membrane, but a clear, gelatinous, more or less
firm layer of the sarcode may be observed to form the outer boundary of the sphere, as
already described in Thalassicolla.

The sarcode of the central capsule is continuous with the external sarcode through
the pores of the dividing membrane. The extra capsular sarcode is usually frothy in
appearance owing to the presence of clear spaces, — vacuoles or alveoli. These alveoli
usually increase in size from without inwards, being largest and most numerous near the
capsule. The outer alveoli have been observed to disappear .at times and to form again.

The pseudopodia of the Radiolaria resemble those of the Heliozoa, being more or less
persistent and not very flexible. In some species they branch and anastomose slightly.
They originate from tiie deepest part of the external sarcode, pass between the alveoli
and through the gelatinous investment into the surrounding water. They may be
retracted and extended.

RHIZOPODA.

9

The " yellow cells " which are almost hi variably found in the Radiolaria, either
within or without the capsule, have been the subject of much speculation. It is not yet
known what their functions are, and it is even doubtful if they are not parasitic plants,
taking their nourishment from the body of the Radiolarian in which they live. After
the death of the animal the yellow cells have been observed to grow and multijsly.

With the exception of a very few species of Thalassicolla, Thalassolam.pe^ Mtjxo-
brachia, and Collozoum, all the Radiolaria are provided with some form of silicious
framework. In its simplest form this consists of isolated spicules, as in Sphcerozoum,
Fig. 9. From the simple spicular forms we may pass to those having s])ines radiat-
ing from a common centre to the surface of the sphere, or beyond, with lateral processes
like Xiphacantha, Fig. 7.

/

Fig. 5. — Eticecryphialus gegenbauri, greatly enlarged.

In certain species the skeleton is formed of hollow spines, through which the sarcode
extends and issues from the ends. In all cases the spines are covered with a thin layer
of granular sarcode, which can be observed constantly flowing up and down the sjaines,
doubtless carrying the food that may be collected, down into the body.

As the lateral processes mentioned above become more largely developed, a con-
tinuous Qircumferential skeleton is formed, which encloses the whole organism, as in
Actinomma, in which there are sometimes three or more concentric shells. Among
the Polycystina there is a great variety of form manifested in the external skeleton.
Podocyrtis (Fig. 8) is one of the most common forms of this gi-oup.

The food of the Radiolaria consists of minute algis, diatoms, infusoria, and other
organisms found on the sm^face of the sea.

Not much is known concerning the methods of multiplication among the Radiolaria.
It may be accepted as an established fact that the contents of the capsules may divide
and form young capsules, which arc at first without any membranous covering. The
young capsules make their way out, swim about freely as " zoospores," whicli, in Col-

10

L 0 WER IN VER TEBRA TES.

losphcera, are oval, about .008 mm. in length, and have at least one ciliiim. The sub-
sequent history of the zoospores has not been made out. It is probable that colonies
like Collosphcera are formed by division of this kind.

In this large and exceedingly interesting order of Rhizopods, there are nearly a
thousand species, about one-half of them being fossil forms. This shows the wonderful
variety of form which such organisms may present without depaiting from the simple
plan or organization which characterizes them. They may be classified according to
the forms of their skeleton, into families and sub-farailies, in which one general plan of
structure Avill be characteristic of each division, as Dr. WaJlich has shown. Although
such a classification may be convenient, it throws but little light upon the physiological
or morphological relations of the different forms. In the present state of our knowl-

FiG. 6. — Haliomma poli/acantimm, magnified 200 times.

edge of the Radiolaria no fully satisfactory classification is possible. Perhaps the best
yet proposed is that of Prof. Mivart, which is a greatly modified form of Ilaeckel's
comprehensive but confusing plan. Prof. Mivart arranges all the Radiolaria under
seven divisions, which may be briefly characterized as follows : —

1. DisciDA. — Discoidal forms with skeletons partly intra-capsular, generally form-
ing an external perforated shell with an internal partition, making a series of connect-
ing, concentric, or spirally arranged chambers ; no nuclear vesicle.

In this group tliere are five sub-divisions, but the most common form of all is the
Astromma, in which the combination of radial and circumferential parts is quite strik-
ing, both for beauty .and for the great variations in form manifested by the different
species.

RHIZOPODA.

11

2. Flagellifeea. — This group receives its name from the flagelhim which charac-
terizes the species belonging to it.

3. Entosph^eida. — In this group the organisms are f>rovided with an intrarcapsu-
lar, spheroidal shell, not traversed by radii, in this respect differing from the Discida.
They have no nuclear vesicle. The typical genus is Ilaliomma, of which there are
many forms. Haliomma polyacanthum is represented in Fig. 6.

4. AcANTHOMETEiDA. — The members of this division are characterized particularly
by a well-developed radial skeleton, the radii meeting in the centre of the capsule. There
is no enveloping shell, but lateral processes sometimes project from the sjjines, as in the
beautiful IKipliacantha found by the " Challenger " expedition, represented in Fig. 7.

Fig. 7. — Xtphacantha, magnified 100 times.

5. PoLYCYSTixA. — The Polycystina are by far the most numerous in all fossil
deposits of Radiolaria. They are very simple forms with skeleton external, more or
less compact or continuous, without a nuclear vesicle. The shell may be a simple
sphere, or two or three concentric spheres connected by radii, or with external radial
outgrowths extending to a length of several times the diameter of the shell. The
most numerous forms, however, belong to the genera Podocyrtis and Eucyrticlium,
the former represented in Fig. 8. The beautiful Eucecryphialus (Fig. 5) also belongs
to this group. In these foi-ms the sheU opens at one end, and growth being mainly
in one direction said to be unipolar.

6. CoLLozoA. — To this group belong a number of soft, gelatinous forms which are
frequently aggregated in colonies, and are therefore designated as compound Radio-
laria. The animals may be either single or in families. When single the skeleton con-
sists of circumferential spicules, isolated from each other. When compound, there

12

LOWER INVERTE'BRATES.

mav be either spicules or a spheroidal, perforated shell. Under this division are classed
the very common forms Sphoirozoum, Fig. 9, and Collosphcera^ the former being
either naked or having spicules, while the latter has a shell.

7. Vesiculata. — To this group belong the curious jelly-like forms already men-
tioned, described by Huxley as ThalassicoUa, Fig. 4. Tliere is no
definite skeleton, but some of the species have spicules more or less
closely approximated. The vesiculata are distinguislied bj' the presr
ence of a nuclear vesicle, which is usually multiglobular. Formerly
the Thalassicollida were classed with the Collozoa, but the nuclear
vesicle is not found in the latter, and there is no external shell or
spicular layer in the former such as are found in Sphcerozoum and
Collosphcera.

When we consider the wonderful sjiiimetry, beauty, and variety

of form revealed by a study of the hard, silicious skeletons of the

Polycystina, Acanthometrida, and other famihes of the order, we

may well inquire how it is possible for such simple creatures to

construct such perfect forms. Mivart suggests that they may be

produced by " a kind of organic crystallization — the expression of

some as yet unknown law of animal organization here acting un-

FiG. 8. — Fodocyrtis trammelled by adaptive modifications or by those needs which seem

enlarged?*'*' ®"*"'' to be SO readily responded to by the wonderful plasticity of the

animal world."

Representatives of the great class Radiolaria are found in all seas, but they are by

far the most abundant in tropical waters. The most common forms of all belong to

the Acanthometrida and Polycystina. Their remains have formed immense beds of

rock, mostly during the Tertiary age, but
they have also been found in the chalk and
in the Trias. They are found in the diatom-
aceous rock of Richmond and Petersburg,
Va., also in Maryland, and in Bermuda ;
but by far the most extensive deposits are
in the Nicobar Islands and the Barbadoes.
In the Xicobar Islands deposit they form
strata eleven hundred and two thousand
feet in tliickness, in wliich a hundred
\-^^'-S^^'^gmwmKmMj^xmmifr'^,^^Bp^^yj^ sjtecies have been identified. In the Bar-
'^^^H^jBlilBBiKffiP^jBMMlB'^^^ badoes the rock is not quite so thick, but

about three hundred species have been
found there, most of which are Polycystine
forms.

A number of minute but very beautiful
organisms were obtained by Mr. Mui'ray
during the "Challenger" expedition by
using the tow-net, which undoubtedly deserve a place among the Protozoa, but they
have not yet been classified. They have been named Challengerida, and seem to be
closely related to the Radiolaria.

^m£:m.^.

Fig. 9. — Spliserozoam ovodimare, greatly enlarged.

RHIZOPODA.

13

Order III. — HELIOZOA.

The Heliozoa, or sun-animalcules, are very beautiful Rhizopods, inhabiting fresh
water. Most of them are spherical, floating forms, but a few are attached by long
pedestals or stipes. The pseudopodia are in the form of delicate, tapering rays, extend-
ing outward in all directions from the centre, often exceeding the diameter of the body
in length. They are flexible, more or less contractile, and sometimes reveal a slow
circulation of granules along their
length. The sarcode is not distinctly
differentiated into endosarc and ec-
tosarc, but in one interesting form,
Aciinosphcerium, the outer sarcode is
a frothy, vacuolated mass of consider-
able thickness.

The most common of the Heliozoa
is the Actinosphri/s sol. It is found in
pools of standing water almost every-
where, among the floating plants, ap-
pearing under a low-power of the
microscope as a colorless, spherical
body, varying in size from .04 mm. to
.1^ mm. in diameter, with innumer-
able delicate, bristling spines three
or four times the diameter of the body
in length. Tlie sarcode is full of vac-
uoles, which give it a frothy appear-
ance. Watching the minute sphere a
few moments, there -will probably be
seen somewhere along the periphery a
slowly distending vesicle, which reaches
a certain size, and then suddenly col-
lapses. This is the contractile vesicle.
The first description of this curious
little creature seems to have been given
by a French naturalist, who referred to
it, if we may translate the bad French
in which it is written, with some dis-
cretion — as "a fish, the most extra-
ordinary that one could see."

The food of Actino2)hrys consists
of minute infusoria, diatoms, and other

unicellular algre, which frequently can be seen within the body as green balls. The
pseudopodal rays are used as organs of locomotion, and for the prehension of food. If
an active infusorian comes in contact with the spines it seems to be paralyzed. If the
prey be very minute it will be seen to glide along the rays very gi-adually until it reaches
the body, when a portion of the sarcode is projected to envelop it, and draw it into the

Flo, 10. — Clathrulina elegans, enlarged 350 times.

14 LOWER INVERTEBRATES.

interior, where it undergoes digestion and assimilation. If the prey be larger, several
rays may bend toward it and together secure and draw it down to the body.

Actinophrys propagates by simple division and by the fusing together of two or
more specimens into a single mass, which then rejjroduces new forms by fission. Tlie
conjugation of two individuals is quite a common occurrence, but the Hon. J. D. Cox
has observed as many as nine individuals joined in the process. The same observer
also describes another method of propagation in which the parent form passes into an
opalescent condition, after which it undergoes segmentation into a brood of young.

A much larger heliozoon, greatly resembling Actinophrys, is Actinosphoerium. It
is especially distinguished from the former by the frothy layer of ectosarc which sur-
rounds the central sarcode, and by the complex structure of the pseudopodal rays
which, under high magnification, seem to have a hard axis-cylinder, probably onl}^ a
core of denser protoplasm.

Perhaps one of the most beautiful forms of this order is Clathrulina, represented
in Fig. 10. While young the capsules are colorless and clear, but with age they be-
come yellow. The sarcode does not usually fill the lattice-capsule, but is collected in
a ball within it. It is a very beautiful species ; often found in great abundance in ponds
and ditches.

The Heliozoa seem to be quite closely related to the Radiolaria, but the exact rela^
tions of the two groups is not yet known. It has been suggested that the Heliozoa are
embryonic forms of the more highly-developed group ; but until the structure of both
groups is more fully elucidated it seems useless to speculate much about this question.
Several observers have noticed within Actinophrys a peculiar nuclear sphere which
gi'eatly resembles the central vesicle of certain Radiolaria.

Order IV. — RETICULARIA.

Sub-order I. — Peotoplasta.

This sub-order includes a considerable number of fresh-water Rhizopods with very
soft sarcode bodies and delicate, branching, thread-like pseudopodia. The endosarc
and ectosarc are even less clearly differentiated than in the lobose forms. The nucleus
is usually large, and several contractile vesicles are to be seen in the endosarc.

A characteristic Rhizopod of this sub-order is Gromia ovifonnis, represented in
Fig. 11. The shell is thin, chitinous, colorless or yellowish, measuring about .115 mm.
in length. A high power of the microscope shows an incessant streaming of granules
along the branching, anastomosing shreds of sarcode, the granules moving outward on
one side and back on the other side of each filament. The sarcode extensions of Gromia
anastomose more freely than is usual among the Protoplasta Filosa, resembling more
closely the Foraminifera m this respect, and the contractile vesicle is near the mouth
of the shell. In fact. Prof. Joseph Leidy, in his monograph on the "Fresh-water
Rhizopods of North America," has placed Gromia among the Foraminifera. The
filose protoplasts seem to be in nowise different from the Foraminifera, except that
the shells of the latter are usually calcareous, and the pseudopodia manifest a greater
tendency to anastomose, and are more granular.

The shells of the filose protoplasts are usually composed of a clear, chitinous sub-

RHIZOrODA.

15

stance, sometimes colorless and transparent, sometimes distinctly colored yellowish or
brown, while still others are covered with grains of sand.
A very frequently occurring

form is Pseudodifflugia. In this
the shell is chitmous, with sand-
grains in some wise incorporated
with it. It resembles Difflugia,
Fig. 3, in every respect except as
regards the character of the pseudo-
podia. In some of the genera the
shells are beautifully marked, and
the neck is often curved so that the
body lies on the side as the animal
crawls alonij.

SXJB-OEDER II. — FOEAMINI-
FEEA.

Fig. U. — Gromla oviformis, enlarged 600 times.

The Foraminifera embraces an
almost innumerable variety of ma-
nne Rhizopods. The reticulate,
anastomosing nature of tlie pseudo-
podia is most striking!}' manifest
in all the Foraminifera, but the ex-
amination of the internal sarcode is
very difficult, owing to the thick-
ness and opacity of the shells. For
this reason it was long supposed
that the Foraminifera were desti-
tute of a nucleus, but recent inves-
tigations by Hertwig and Lesser,
Carpenter and others, have revealed nuclei in several forms, and they are doubtless
present in all of them. It is said that dahlia violet will stain the nuclei while the
animal lives, and if this is true in all cases, it will prove a valuable reagent in further in-
vestigations of those organisms.

The Foraminifera are the only Rhizopods that have shells of many chambers, and
of complex structure. The different forms of the shells can best be understood by
observing how they are derived from a single chamber by the budding off of successive
j)ortions of the sarcode-body, each of which then secretes a shelly covering. If the
budding always takes place in the same direction, an elongated form composed of
several chambers in a straight line is produced, as in JLagena. If the tendency of
growth is to produce a spiral, it results in the beautiful Connispira, which greatly
resembles the mollusc Planoiins, or, if the budding takes place in still another way,
the more complex forms of MiUola are produced, which are only spirals greatly
elongated in one direction. Instead of forming successive single chambers at the ends
of old ones ; the growing spiral may spread out wide and flat, thus forming the beauti-

16

LOWER INVERTEBRATES.

Fjg. 12. — PeneropoUs, enlarged.

ful Polystomella, and PeneropoUs., Fig. 12, common in all tropical seas. In the Ber-
muda sands the most frequently occnrring genera are PeneropoUs, Fig. 12, Orhicu-
lina, and OrbitoUtes, Fig. 15. Tliese, with other light debris, are occasionally washed
out of the heavier matters of the shore by the action of the waves, and left in great
abundance in long, white streaks as the waves recede.

Among the spiral shells there are two types, distin-
guished as nautiloid and turbinoid. When the spiral forms
in one plain, as in Polystomella, we have a nautiloid spiral ;
when it winds obliquely around a vertical axis, forming a
spiral like the snail or periwinkle, it is turbinoid. The
beautiful liotaUa, Fig. 13, is formed upon the latter plan.
In most of the rotaline forms, all the chambers of the whorl
are visible from one side, but among the spirals of the
nautiloid type the later chambers often more or less en-
velop the older ones, so that unless one knows the struc-
ture of the shell it cannot be recognized by a cursory or superficial examination.
For example, in the very frequently occurring N^onionina, the older chambers are
quite invisible, being entirely enveloped by the later ones, and in order to learn how
the shell began to form, a section would have to be made through it showing all the
chambers in one plane.

Among the turbinoid spirals, there are several varieties of structure, the relations of
which are not easily seen until careful examination of the in-
ternal structure reveals them. Thus, Textularia, Fig. 14,
belongs to the division, but at first glance it scarcely seems to
bear any relation to Nonionina.

On close examination it will be seen that the successive
chambers are ui two rows, and each chamber communicates
with the chamber above and the one below it on the other

^ „ „• • , 1 1 r ■. Fig. 13. — 7io/a/irt, enlarged.

row, never ojsening into a chamber of its own row.

In some species the nautiloid spire is characteristic only of the early period of
gi'owth, for after a few turns, instead of budding from the end, thus continuing the
sj)iral, all the outer chambers put forth radial buds, which form successive concentric
rings. This mode of growth is well illustrated in OrbitoUtes, which is represented in
Fig. 15, part of the surface being removed to show the internal struc-
ture. It Avill be seen that the internal chambers are spirally arranged,
while the others are arranged on the cyclical or radial plan of growth.

Dr. William B. Carpenter, whose valuable monograph on the Fora-
minifera has tlirown much light upon the structure and relationship of
these organisms, has shown the great importance of a careful study of
the shell-structure as a basis of classification. He has distinguished two
kinds of shell among the Foraminifera, which he has designated, re-
spectively, the porcellanous and the h_yaline, or vitreous. These differ-
ences of shell-structure correspond with jjhysiological differences in the
organisms inhabiting the shells, and afford a basis for a division of the
class into two great sections. In both these sections will be found species which
have striking resemblances in form, which could not be generieally separated except
by a recognition of the differences in the structure of the shell and their jshysiological
si"nificance.

Fig. 14. — Textu-
laria.

extended, enlarged 200 times.

RHIZOPODA.

17

The terms porcellanous and vitreous have been adopted owing to the appear-
ance of the shells as seen under the microscope. The former is applied to shells
of a white, opaque, often shiny appearance, which in thin, transparent sections or
laminse appear, by transmitted light, of a brown or amber color. No structure can
be observed in shells of this kind. They are never perforated, although they are
sometimes marked upon the surface with pits, or inequalities, giving an appearance
of foramina.

The vitreous or hyaline shell-structure is far more complex than the porcel-
lanous. It is transparent, usually colorless, sometimes deeply colored, and more or
less closely perforated either with large or small distinct foramina, or minute tubuli
passing directly through the shell-substance. In Motalia, Fig. 13, the foramina are
distinct, and afford passages for the sarcode, which covers the outside of the shell,
and the pseudopodia extending in all directions from it. The minutely tubular
structure can only be detected in thin sections with high powers of the microscope,
when it imparts a peculiar appearance to the shell, characteristic of finely tubular
structures.

Between the shells with large foramina and with minutely tubular structure, there
is a continuous gradation, which
indicates that both foramina and
tubuli subserve the same pur-
pose, — affording channels for
the passage of the sarcode.
Comparing the shells of the
porcellanous and vitreous forms,
it will be seen that while the
pseudopodia of the animals oc-
cupying the former all spring
from the terminal or outer
chambers alone, so that the
nourishment for the sarcode
of the inner chambers must
pass in through those that in-
tervene, in the vitreous forms
the sarcode of each chamber is

in direct communication with the outer world through either the foramina or the
minute tubuli of the shell. In accordance with this difference in the structure of
the shell-substance, it may be also observed that the stolons of sarcode connecting
successive chambers of the porcellanous-shelled species are njuch larger than those in
the vitreous-shelled forms.

These facts may be best illustrated by comparing two of the most highly-developed
forms of the two types of shell-structure. For this purpose we will select OrUtolites
of the porcellanous, and Niommulina among the tubular-shelled forms.

The structure of OrUtolites can be understood by a glance at Fig. 15. Disks such
as are here represented sometimes attain the size of a silver quarter-dollar in diameter.
It will be seen that single pores unite successive chambers, and finally the sarcode of
the outer chambers communicates with the surrounding medium by pseudopodia pro-
jected through the marginal pores shown in the figure.

In Mmwwlina, a form that has been so abundant in the past as to have lent its

VOL. I. — 2

Fig. 15.

■ OrUtolitts, enlarged. Diagram to show external appear-
ance and internal structure.

18

L 0 WEP, IN VER TEBRA TES.

name to the nummulitic limestone, the tubes have a different arrangement and are
very minute ; there is, besides the tubuhir structure ah-eady described, a system of
inoscuhiting canals penetrating the septa, which are filled with sareode during the
life of the animal. In all the vitreous forms, each chamber has its own shelly in-
vestment, so that the partitions between the chambers are double. Between these
walls there is frequently a considerable deposit of calcareous sulistance, which is

known as the intermediate skeleton. Through the

intermediate skeleton runs the system of canals,

X<5>}^ ^^ II ^^^^M^J^^^l which is beautifully shown in Eozoon. soon to be

described ; the canal-system resembhng minute
branching shrubs. A single species of Nmmnu-
Fio. 10. — A«nimi(/iHre wiicox'i, natural size, lina^ Fig. 16, has been described from Florida.

aud enlarged. -r-» • -i i ■ ■ c i n i

Isesides the two varieties of shell-structure above
described, there is another kind of shell or test very frequently occurring among deep-
water species. This is the arenaceous type, in which the shell consists of cemented
grains of sand, or of sand and spicules together.

The nature of the cement which holds together the sand-grains of the arenaceous
tyi^es is not known ; sometimes the grains are only loosely united, so that the test is
more or less flexible, as in Astrorhiza, Fig. 17, a form which is found in Vineyard
Sound at depths of only twelve fathoms, but also reaching down to over five hundi-ed
fathoms. Some of these have the outside test smoothly plastered by a layer of very
fine i)articles of mud, although composed of irregular large and small grains of sand.
No definite ajierture, or mouth, has been observed in Astrorhiza,
and the sareode finds its way through the test between the loosely
cemented grains composing it. In other forms the grains are
very closely cemented, so that some tests ■will resist the action
of warm nitric acid, proving that the cement is neither calcareous
or ferruginous. In some cases the sand-grains seem to have a
chitinous basis in which they are imbedded. The resemblance
between the arenaceous Foraminifera and the porcellanous and
vitreous species is striking. Take, for examjile, Ilalophrag-
mium, and compare it with Globigerma, Fig. 18.

Indeed, it is true that if we consider only the external forms,
we can find in the three divisions of porcellanous, vitreous, and

arenaceous forms many species that are so closely related as to be indistinguishable
by any specific characteristics. Thus, Cornuspira among the porcellanous is the
counter-part of Sjm-illina among the vitreous forms ; and this is distinguishable in
form from Amniodiscus among those with sandy tests.

While some of the tests of the arenaceous group are probably imperforate, others
are, without doubt, more or loss porous, so that the distinction already made Ijetween
hyaline and jwrcellanous forms must also hold good as concerns these. Indeed, cer-
tain arenaceous forms liave no definite mouth, and the sareode must find its way
through pores in the test.

The deep-sea investigations that have been carried on of late years have brought to
light many new forms belonging to genera which were sup)wsed to be very well known.
Thus, the shell of Glohigerwa, Fig. 18, has been understood, conforming to the descrip-
tion of Dr. Carpenter, to consist of a series of hyaline, jierforated, spheroidal chambers
arranged in a spiral about an axis, each opening into a central space in such a manner

\i

Fic. 17. — Astrorhiza, en-
larged two diameters.

RHIZOPODA.

19

that all the apertures are visible when looking into the common vestibule. But in
the light of more recent investigations, Mr. Brady has found it desirable to enlarge
the scope of the family to include many new species. He has, therefore, divided the

Globi

Fig. 18. — Globitjerina bulloides, greatly enlarged.

bigerinxB into three groups, according to the position ami ai)pearance of the apei'-
tures, as follows : —

1. Forms with an excavated cavity (umbilical vestibule) into which the orifices of
all the segments open, such as Glohirjerina bulloides, Fig. 18.

2. Those with only one external orifice, situated on the face of the terminal segment,
at its point of junction with the previous convolution, as in Globigerina influta.

20

L 0 WER IN VER TEBRA TES.

3. Forms in which tlic inferior aperture is single and relati-\-ely small, but supple-
mented by conspicuous orifices on the superior surface of the shell, as in Globigerina
rubra.

Besides these, there are forms represented under the generic name Orbtdhia, 'which
seem properly to belong to the Globigerince, as sub-generic forms. Orbulhia has a
spherical shell, usually without a definite mouth, but provided with two sets of perfo-
rations differing in size, — one series numerous and minute, the other larger and less
numerous.

Closely allied to the Globigerina, if not properly belonging to that family, is the
beautiful Hastigerina tnurrayana, found by the "Challenger" expedition. This organ-
ism was foimd long ago by D'Orbigny (1839), and described by him as yonionina
pelagica, and was one of the first Foraminifera taken at the surface of the sea.

The Foraminifera inhabit the sea, and their remains are graduallj^ forming rocky
strata on the ocean-bed, in all respects like the chalk of the cretaceous period. For a

long time it was supposed that the Foraminifera
found at the bottom of the sea passed their entire
life there. Prof. Wyrille Thomson held firmly
to that opinion until the results of collections with
the tow-net at the surface conclusively proved that
many of them live near the surface. It is now
known that a few species of Globigerina inhabit
the superficial waters, but a far greater number
pass their life at the bottom.

The jielagic forms of Globigerina are usually,
liut not always, spmous. The long, delicate spines
are somewhat flexible, and clothed «-ith granular streaming sarcode ; and for some
distance from the shell tlie frothy sarcode fills the spaces between them. The spines
are so delicate that a mere touch will break them off, and spinous sliclls are never
seen in material brought up in the dredge. Sometimes the spines are very long ; in
Hastigerina mwrayi the si)ines are fifteen times the diameter of the shell, and the
frothy, alveolar sarcode extends outward between the sj:)iues to a distance equal to twice
the diameter of the shell.

The Globigerina are so abundant in some places, and their remains constitute so
large a proportion of tlie shiny calcareous ooze covering a great part of the sea-bottom,
that the ooze has long been designated " Globigerina ooze." The Globigerina ooze
consists of the remains of Globigerina and Orbxdina in great abundance, with a smaller
])roportion of the genera Pullenia and Sphcerodina, with occasional sjiecimens of Ilas-
tigerhia, together with remains of radiolarians, diatoms, and some curious structures
known as rhabdoliths and coccoliths, the nature of which is not yet understood.

As regards the distribution of the remains of protozoic life over the ocean-floor, it
appears that the Gloljigerina ooze extends from four hundred down to al)out two thou-
sand fathoms. Bej^ond this limit there seems to be a gradual disintegration and solution
of the calcareous substance of the shells, resulting first in a gray ooze down to two thou-
sand three hundred fathoms, containing no perfect shells, but some calcareous matter
effervescing with acids, finally changing as we go still deeper to an hupaljiable red
feldspathic mud, or " red clay," as it has been termed, which covers vast areas. The
red clay is supposed to bo derived partly from the disintegration of the shell-matter of
the gray ooze and the solution of the calcareous portions, and partly from the mineral

Fig. 19. — Helixostegiiie forms of Foraminifera.

RHIZOPODA. 21

matter held in suspension in tlie sea-water, which slowly sinks to the undisturbed
depths.

Nevertheless, the deepest ocean-floor is not always devoid of organic remains. The
deepest soundmg by the " Challenger " was made in the Pacific Ocean on the 23d of
March, 1875, and showed a depth of four thousand five hundred and seventy-five
fathoms. The bottom was covered with what resembled the ordinary red clay to the
eye, but it was gritty, and contained sueli a large jiroiiortion of radiolarian remains
that it received the name of Radiolarian ooze. It liad previously been supposed that
even these silicious remains, together Mitli the frustules of diatoms, which are more or
less al)undant in the Globigerina ooze, disaiipeared ^nth the calcareous shells, in some
manner not fully understood. The occurrence of the deep Radiolarian ooze, however,
has sliown that there is no destruction of silicious shells, and their accumulation in so
nuicli greater alrandance there than in the Globigerina ooze was accounted for by Prof.
"Wyville Thomson on the supjiosition, based u])on the results of collections at different
depths down to one thousand fathoms with the tow-net, — that Radiolaria lived at all
depths, and therefore, where the water was deepest the accumulations of their skele-
tons would be the most rapid. Later investigations by Mr. Agassiz, using an ingenious
apparatus devised by Lieut.-Commander Sigsbee, U. S. N., have shown that there is
no life between a narrow zone where the surface animals are found and the habitat of
those living on or very near the bottom.

The deepest oast that has ever been made was made from the XJ. S. Coast Survey
Steamer "Blake" in January, 1883, in latitude 19° 39' 10-/ N., and longitude 66° 26-
05" W., between the Bermudas and the Bahamas, about one hundred miles N. W. of
St. Thomas. The dejith there found was four thousand five hundred and sixty-one
fathoms ; the temperature of the deepest water was 36° F. Another cast in latitude 19°
29' 30" N., longitude 66° 11' 45", showed a depth of four thousand two hundred and
twenty-three fathoms. At these great depths, — more than five statute miles beneath
the surface, a depth equal to the height of the highest mountains in the world — tlie bot-
tom is covered with a very fine brown ooze, containing a few Diatoms and sponge
spicules.

In the North Pacific, at depths of three thousand and four thousand fathoms, are
found tests of Trochainmina {Ammodiscus) incerta, one of the arenaceous forms. At
great depths are also found species of Ifiliola, tisually more or less incrusted with
grains of sand, while in some cases the shell consists not of lime, but of clear, homo-
geneous siUca which will resist the action of acids like the frustules of diatoms.

Some of the genera of Foraminifera have had a great range in geologic time. In
the lower Silurian rocks of Russia — in the so-called Ungulite grit — Elirenberg found
green sand casts of genera now living, Textidaria, Gattulina, and Rotalia. The
oldest form of life of which the rocky strata furnish any remains is possibly the Eozoon
Canadense, found preserved in greatest perfection in the Laurentian rocks of Canada.
Concerning the nature of Eozoon — the dawn-animal — there lias been much contro-
versy. On the one hand it is claimed with great probability that the peculiar struc-
tures found in the rocks are of purely mineral origin. But Dr. J. W. Dawson and
Dr. "William B. Carjienter, who have studied this subject with great care, have
declared that the structure of Eozoon. corresponds in every particular with that of cer-
tain Foraminifera of the vitreous type. The successive chambers connected by pas-
sages, the intermediate skeleton with its comjilex system of inosculating canals, the
minutely tubular " nummuline layer," have all been claimed to have been found and

22 LOWER INVERTEBRATES.

studied -with great, care. The Eozoon occurs iu a serjientine limestone, in the form of
irregular masses of varying size up to several inches in diameter. In appearance to the
naked eye it consists of alternate bands of green serpentine — a silicate of magnesia —
and limestone, the former filling the cavities originally occupied by the sarcode, and
even the most minute tubuli of the nummuline layer; while the calcareous basis of the
original skeleton remains unchanged.

The simplest, and on the wliole the most satisfactory, method of studying the
Eozoon is to cut tolerably thin slices of the rock and place them m a verj- dilute acid
until the calcareous portion is dissolved. There then remains a perfect cast of the
chambers of the shell, counterparts of the original sarcode-body, even to the mmute
tubules of the nummuline layer. We have given here the gist of the account of Drs.
Dawson and Carpenter, but the question of the animal nature of Eozoon is far from
settled ; possibly it never will be.

In South Carolina there are immense beds of marl aud limestone containino- For-
minifera in great abundance. Prof. J. W. Bailey, in the year 1845, examined some
borings from a well driven through these deposits at Charleston, and also some fi-ag-
ments from an outcrop on Cooper River, about thirty-five miles above that place.
From the borings it was observed that from one hundred and ten to more than three
hundred feet in depth the Polythalmia were abundant, very perfectly preserved, and
many of them large enough to be easily seen with a pocket-lens. Concerning these
tertiary deposits, Prof. Bailey remarked that they were filled with more numerous
and more perfect specimens of these beautiful forms than he had ever seen in chalk or
marl from any other localit}'. Similar marls are also found in Virginia, on Pamunkey
River, belonging to the eocene ; and in the miocene rocks of Petersburg, Foraminifera
are also found.

The foraminiferal rock which underlies so large a part of South Carolina is still in
process of formation along the coast. The mud from Charleston harbor abounds in
shells of Foraminifera, and the remains of diatoms.

Fossil Foraminifera are found in many other places in this country. They exist in
New Jersey, Alabama, at various points on the Missouri and Mississippi rivers, in Ten-
nessee, Arkansas, North CaroUna, Florida, and elsewhere. The marls of certain
localities along the upper Missouri and Mississippi rivers are very rich in Foraminifera.
The latter deposit is popularly known as " prakie chalk," and the forms are different
from those found on the Missouri.

In the green sands of Fort Washington, Va., Prof. BaOey made the remarkable
discovery that these minute and perishable organisms could be entirely destroyed by
chemical changes, yet leave indestructible memorials of their existence in the form of
mineral casts. Ehrenberg had previously observed that the lime of the shells could be
gradually dissolved and replaced by silica. In flints such a replacement is not un-
usual, and remains of shells thus mineralized can be obtained by treating the rock with
acid, which leaves the silicified shells intact.

But in the green sands of the chalk formation in New Jersey, Virginia, and else-
where, the shells have become filled with a greenish mineral, glauconite, — a silicate of
iron and potash of varying composition — which has followed every contour of the
shell, and penetrated even the minute pores and tubuli so perfectly that the genus and
even the species of the Foraminifera can be readily determined by a study of the glau-
conite casts after the shell has been destroyed.

The glauconite occurs in grains scattered through the green sand formation of the

GREGARINIDA.

23

cretaceous and other periods. In many cases the gi-ains are found to be casts of Forar
minifera. These constit\ite as mucli as ninety per cent, of some rocks. In the yellowish
limestone of Alal)ama such casts occur in great perfection, constituting about one-third
of the rock. To obtain them, the stone has only to be treated with acid, when the
greenish casts can readily be picked out from the insoluble residue, consisting of sand
and finely-divided mineral particles.

Ehrenberg was the first to observe the replacement of organic forms by mineral
matter, and he inferred that green sand was always formed by such a substitution.
Such easts can be found in limestones from Mullica Hill, and near Mount Holly, N. J.,
from Drayton Hill, near Charleston, S. C, from the cretaceous rocks of Western Texas,
and from other localities.

At the ]n-esent time precisely similar casts of Foraminifera are being formed at the
bottom of the sea. In the year 185.3 Count Pourtales found, off the coast of Georgia,
in the Gulf Stream, at a de])th of one hundred and fifty fathoms, a bottom dejjosit
consisting of shells of Glohigerina and black sand in about equal proportions. Similar
deposits were found also in the Gulf of Mexico and in various parts of the Gulf Stream.
With them are also found the living Foraminifera, so that there can be no question as
to the continuance of the process now.

RosiYN Hitchcock.

Class III. — GEEGARINIDA.

The Gregarinida are a peculiar kind of animal parasites which inhabit the intestinal
canals of earthworms, insects, Crustacea, etc., the simplicity of whose structure leads
most authors to class them among the Protozoa. Their distinct mem-
branous investment, however, entitles them to a higher rank than any
of the Protozoa already described, and, although with very little power
of movement, and j)ossessing no means of searching for and collecting
food, they are still structurally higher than the Amceba and its allies,
for a differentiation of parts is certainly distinctly shown in the mem-
branous cell-covering. As parasites they do not require to move about
in search of food. They have no mouth, no organs of digestion. They
absorb their food through the membrane that covers the body ; hence,
although they are structurally abo\'e the Amoeba, they have almost lost
the Amoeba's power of voluntary movement. We may conceive of an
Amoeba placed under conditions that would insure an abundant supply
of food without the necessity of searching for it, finally losing its power
of movement and developing a distinct membranous investment from
the ectosarc. We would then have a Gregarine. Van Beneden has regarded the
Gregarinida as AmoebiE thus degenerated by parasitism. But there has been no degen-
eration of structure, only of habit ; it will be seen that Gregarines are all auioeboid in
one stage of their development, and that from this larval condition the more highly
differentiated adult is produced.

The Gregarinida vary considerably in form and appearance, but in general terms
they may be described as more or less ovate or cylindrical in form, the body consisting

Fig. 20. — Ctepsi-
(Irina munerif
enlarged.

24 LOWER INVERTEBRATES.

of a single cell frequently divided into two or more portions by transverse, internal
septa, forming the antei'ior and posterior sacs. In some species tlie anterior end, or
head, is furnished with a circle of rcflexed hooklets, in others no such armature is found.
The membrane covering the body is transparent and structureless in ajjpearance.
Although firm and elastic, it is very permeable to watery fluids. The contents of the
body are a nucleus embedded in the protojilasm and fatty granules. The latter are
usually so abundant as to give a milky appearance to the cell contents. The granules
seem to increase in size and abundance as the animal matures, since in young individ-
uals they are scarcely noticeable.

The nucleus invariably present in all Gregarines is a s]iherical vesicle with a sharply-
defined membrane, situated near the middle of the cell in the Monoeystidea and in the
forward part of the posterior sac of the Dycistidea. A nucleolus is usually found
within it.

When about to multiply, tiie GregariniE become surrounded by a transparent coat
or cyst, which may include either a single specimen or two together. After becoming
encysted a change takes jilace in the enclosed Gregarines. If two of them are in
the cyst they become united, lose their identity and merge into a single mass. From
this mass nucleated cells soon develop, which gradually take the form of elongated
bodies, tapering at both ends, greatly resembling certain diatoms known as JVaviculce,
whence they have taken their name, pseudo-naviculfe. They are also known as
psorosperms. Finally the membrane of the cyst is ruptured and the pseudo-naviculte
escape.

Tlie process above described is not the only one by which the spores are formed,
even in the same species. At least two others are known, one a ])rocess resembling the
segmentation of an egg, in which the entire mass is converted into very regular and
granular sj^heres of segmentation, which in turn becomes elongate and covered with a
firm investment, while their contents become more fluid ; another in which the con-
tents, instead of jiroducing granular spheres, divides into two, four, or more parts, each
of which, by a process not understood, becomes covered with a layer of transparent or
slightly granular globules, and these parts are transformed into the spores.

In some instances the cysts of Gregarines have been observed arranged in a linear
series in the walls of the rectum of certain animals, and it was for a long time a gi"eat
mystery how they could be thus regularly placed. Van Beneden observed in the rec-
tum of a lobster as many as seven cysts in a linear series. The Gregarine of the lobster,
Poros2}ora giyanteu, attains the extraordinary length of 16 mm. and .15 mm. in diame-
ter. During the ])roper season, sj^ring and summer, it is very abundant in the intestine
of the lobster — at least in lobsters from certain localities — as many as twenty-five
being sometimes found in a single individual. At this time no cysts can be found, but
in the autumn the parasites seem to ])ass down into the rectum, where they become
encysted. The general process of encystment is somewhat as follows : —

The contents of the cyst are always at first granular, forming a single sphere with-
out a nucleus. By division, two rounded masses next appear, and as the diameter of
the cyst increases, these separate, and a clear, colorless liquid surrounds them. The
wall of the original cyst then, at least in P. </ic/antea, becomes granular and disappears,
while the two globes become surrounded by firm membi-anes, and their contents may
again divide like the parent cyst. In other words, the cysts are capable of multiplica-
tion by division through successive generations. It is by the nuilti]ilication of the cysts
that their linear arrangement is brought about. Eventually the cysts cease to divide,

GREGARINIDA. 25

and pseuclo-naviculffi are tlieii produced. We have now to follow the development of
new generations from tliese spores.

The development of the pseudo-navicul.T has not been fully made out, except in a
few cases. It is probable, however, that their granular contents escape, and form
amoeboid masses from which the Gregarines are either directly or indirectly developed.

In the intestine of the lobster naked protoplasmic masses have been observed,
which, as will be seen, have been proved to belong to the Gregarines. In the perivis-
ceral cavity of the earthworm the encysted Gregarines, Gregarina lumhricus, are often
found in great abundance. There the pseudo-naviculaj are set free in innumerable
quantities, and their contents have been observed to jiroduce amoeboid bodies from
which new generations of parasites originate.

The Gi'egarins of the lobster, P. gigantea, according to E. Van Beneden, develoj^s
from an amceboid form, but the course of delevopmont differs somewhat from that
observed in the case of the Gregarine of the earthworm. Within the intestine of the
lobster the minutely granular amoeboid form from which the parasite develops was
found destitute of both nucleus and membrane, rGnembXmg Protmnmba 2}rimitiv!a, ov
P. agilis, Haeckel, but not projecting true ])seudopodia. These amajboids become
converted into spherical, motionless globules, the "generative cytodes," which finally
develop two projecting processes, resembling the stalk of JVoctiluca, from which the
Gregarines are directly developed. One of the prolongations is longer than the other.
The longer one sejjarates from the cytode and then moves about independently, like a
nematode worm. The shorter arm then develops, appropriating the entire substance
of the cytode, and likewise acquires the form of a nematode worm. These the author
has designated " pseudo-filari.'B." After some changes in form they cease to move, a
nucleolus and then a nucleus forms about the middle of the body, and finally a new
Gregarine is developed directly from them.

In the development of the Gregarinida we find a complete genealogical, phylo-
genetic history of the cell. From the psorosperms are derived plasmic bodies, devoid
of nucleus or external envelope, allied to the plastidules of the Monera, already described
on page 3, naked cytodes, which are the lowest and simplest forms of living matter.
Then a denser layer of sarcode is formed, corresponding to the ectosarc of rhizopods, but
still there is no nucleus. Soon a nucleus and nucleolus is differentiated from the proto-
plasm, and the cytode becomes a perfect cell. This transformation may take place
directly, or, as in the case of Psoros2xrma gigantea, by the budding of the cytode and.
the develojjment of nuclei within the separated buds. The cycle is completed by the
growth of the young Gregarine, its encystmcnt, and finally the production of the psoro-
sperms.

The Gregarinas are divided into two divisions, Monocystidea and Dicystidea, accord-
ing as the body is composed of one or two sacs. Schneider, who has given the most
com])lete account of these forms, recognizes eighteen genera of Gregarinse, represented
liy about thirty species. Our American forms have been scarcely touched, Di-. Leidy
alone havinur investigated them.

RoMYN Hitchcock.

26 LOWER INVERTEBRATES.

Class IV. — INFUSORIA.

The Infusoria are the highest of the Protozoa. They are so regarded because they
usually have a definite shape, owing to the fact that the outer jJortion of their bodies is
much more dense than the inner. It may, in fact, be said, with slight freedom in the
use of words, that they are surrounded by a skin, or, to use the term of science, an ecto-
sarc ; the jirolongations of their protoplasm for the purpose of locomotion and prehen-
sion are permanent, not transient, as in the pseudopodia of the groups just passed,
extended or withdrawn at j)leasure. In all but the lowest the food is received into the
body by one or more mouths ; and, with rare exceptions, they are active in their move-
ments. Additional points of superiority will be seen further on.

Few Infusoria are individually visible without the aid of a microscope ; but some-
times they form large colonies, which are readily seen. All are aquatic, and wherever
standing water apjjears there are Infusoria. " They abound in the full plenitude of life
alike in the running stream, the still and weed-grown pond, or the trackless ocean.
Nay, more, . . . every dew-laden blade of grass supports its multitudes, while in the
semi-torpid, or sporular state, they permeate as dust the atmosphere we breathe, and
beyond question form a more or less considerable increment of the very food we
swallow."

Anthony van Leeuwenhoek has the honor of first publishing an account of an infu-
sorian. His " Obs. . . . concerning little animals observed in Rain, Well, Sea, and
Snow Water, as also Water wherein Pepper had lain infused," appeared in the Philos-
ophical Transactions, Vol. XII., 1077 ; the recorded discoveries were made during the
two previous years. In Observation I. (1675), four forms are described; of the first he
says, " The first sort by me discovered [in rain-water which had been standing four
days] I divers times observed to consist of 5, 6, 7, or 8 clear globules. . . . When
these animalcula, or living atoms, did move, they put forth two little horns, continually
moving themselves ; the place between the horns was flat, though the rest of the body
was roundish, sharpening a little towards the end, where they had a tayl near four
times the length of the whole body." There is no difficulty in recognizing by this
description a species of Vorticella. It adds fresh mterest to these charming animalcules
to know that they were the first of their numerous kindred to be discovered.

The name " Infusoria " was first used by M. F. Ledermiillcr in 1763. Until quite
recently it was apj^lied to a heterogeneous assemblage of minute animals and plants
having little in common but minuteness. The limits of the group are now pretty well
defined ; there are still differences of ojiinion concerning certain forms, but all students
of the Protozoa now agree to relegate the diatoms, desmids, and rotifers to other and
very diverse relations. The structure of the individual mfusorian as at present limited
will now be discussed.

The zooids of this group of the Protozoa are essentially unicellular ; in the lowest
forms they may consist of a naked cell {gyrnnocyta), or in the higher they may possess
a cell membrane (lepocyta). Ehrenberg held that they were complex or multicellular;
but this view resulted fi-om his "polygastric " theory, put forth in 1830, which has been
shown to be not well founded. Among the distinguished investigators who have also
advocated the multicellular theory, may be mentioned Diesing, O. Schmidt, L. Agassiz,

INFUSORIA. 27

and Claparede and Laclimann. The unicellular theory was first formally opposed to
that of Ehrenberg by Siebold in 1845. It was advocated also by Schleiden and
Schwann. Haeckel has pointed out that the life-history of an infusorian, even one of
the highest, is only an epitome of the life-history of a simple cell. Kent, in his Manual
of Infusoria (1880) holds " that all infusorial structures possess a unicellular morphologic
value only." It seems to tlie writer tliat most living students of the Invertebrata hold
this view.

The bodies of the lowest members of the group (for example, 3fastigain(xba
simplex) are composed of simple protoplasm, exhibiting little or no difference in
density between the inner and outer portions ; in fact, their shape is but slightly more
constant than certain Am<xb(e ; the possession of a flagcllum alone pointing out to the
observer that the object under the assisted eye is not a rhizopod. On the other hand,
those of the higher members of the group, as the Voiticellidae, Fig. 44, have clearly more
dense external layers, either of naked protoplasm or of the same surrounded by a
cuticle of formed matter. Haeckel has described four distinct layers present in the
bounding walls of the highest typical forms. The first is an outer, delicate, hyaline,
elastic membrane ; this in the sedentary, stalked species, extends down
as the sheath of the pedicle, while in others it takes jiart in the forma-
tion of the carapax, as in Euplotes. As secondary products also may be
mentioned the loricae of Cothicrnia and its allies (Fig. 21) ; again, mOph-
rydhtm, it surrounds the zooids as a thick mucilaginous sheath, binding
thousands of individuals into colonies. The second is a highly contrac-
tile layer just beneath the cuticle, called the ciliary layer; from this arise
the cilia and their various modifications. The third, found only in the
highest Ciliata, is termed the muscular layer ; it is jirolonged through the
stalk of Vorticella, giving that organ its eminently muscular function ; ^^^a^puSifa^^
it is highly developed in Stentor and in fSpirostomum ; in the former the
fibrillre are arranged longitudinally, in the latter they have a spiral disposition. The
fourth of these layers is that in which the trichocysts (rod-like bodies possessed by cer-
tain forms) are generated.

The contents of the complex bounding wall, or ectosarc, consists of the more fiuid
protoplasm of the organism. This transparent, colorless sarcode, the endosarc, contains
numerous minute dark-colored granules, food particles, oil globules, foreign bodies, and
an important body which requires special notice, the nucleus. This is usually a more
or less oval body, differing somewhat from the surrounding protoplasm in density, etc.,
and in the fact that it is stained moi'e readily by reagents, thus enabling the observer
to easily distinguish it. In many cases, particularly among the simplest Infusoria,
Huxley says, that "the 'nucleus' is a structure which is often wonderfully similar to the
nucleus of a histological cell ; but as the identity is not fully made out, it may better be
termed endoplast" While it has not been absolutely settled that this body is a true
nucleus, there does not appear to be any valid objection to the view which would
homologize the nucleus of the Protozoa and Metozoa. There are various special forms
of the nucleus: it is sometimes ribbon-like, or coiled into a short, loose spiral (Fig. 44, A),
or moniliform, that is, composed of nodular or oval bodies se])arated by constric-
tions; this form occurs in Sptirostomuni ambiguum (Fig. 22). The nucleolus or en-
dopliisttile, when present, is, in the spherical forms, enclosed witliin the nucleus,
while in the sausage-shaped nuclei it is often outside, attached to the lateral wall.
It has been demonstrated beyond question that in the more complicated types this

28

LOWER INVERTEBRATES.

Fig.

- Spirostomum ambitfuum, greatly enlarged.

organ is enclosed in a membrane. The func-
tion of tlie nucleus will be referred to fur-
ther on.

The contractile vacuole is present in the
majority of species. There may be only
one (the usual condition), or several, and
in rare instances many; in AmjMIejJtus
anser there are from ten to fifty, arranged
in two longitudinal series. It is an interest-
ing fact that the pulsations of these vacuoles
occur, first on one side, and then on the
other, jirogressing from the anterior to the
posterior end of this elongate form. The
vacuole may be simple or quite complex.
When simple it is more or less spheroidal;
in an active animalcule under the micro-
scope it may be seen to steadily fill -i^ith a
clear, watery fluid ; when the full size is
reached it suddenly collapses, after which,
often, no trace of it appears until it begins
again to fill ; the pulse is rhythmical when
the animal is expanded seeking food.
Among the complex types may be men-
tioned those spherical forms with two or
more radiating sinuses or diverticula. In
Paramecium aurelia (Fig. 37), there are
usually from five to eight of these blind
canals; in Stentor 2Mli/?nor2yhus (Fig. 42,
c>}.), a sinus extends from the bulb situ-
ated near the anterior border down to the
foot, while another branch extends from
the bulb about the peristome; in Spiros-
tomwn urnhii/uimi (Fig. 22) it is somewhat
similar to that in Stentor, taking the form
of a lateral canal with a very large bulb
at the posterior extremity; it is often en-
larged also at the opposite end. Con-
cerning its use, whether it is a true organ
with bounding walls, or whether it connects
with the external water, there has been
much lively dispute; indeed, students are
still divided in their opinions of these ques-
tions. Ehrenberg regarded it a spermatic
gland, Dujardin attributed to it a respira-
tory function, Clajiarede and Lachmann a cir-
culatory function. Stein excretory. Huxley
remarks that its function is entirely unknown,
though it is an obvious conjecture that it

INFUSORIA. 29

ma\' bo respiratory or excretory. Kent considers it fully established that there is con-
stant and free intercommunication with the outer water; that it is a mere pulsatino-
lacuna in the cortical layer of the ectojilasm, and that its leading function is excretory,
getting rid of the large quantity of fluid brought into the body by the ciliary or other
currents incident to the capture and intussusception of the food.

The contractile layer of the ectoplasm, i. e. that just beneath the cuticle, bears
permanent prolongations which are the organs of locomotion and prehension; hence
they must pierce the cuticular layer to come in contact with the surrounding medium;
they are long, slender, and represent three well-marked forms, viz. : flagella, cilia, and
tentacula. Tlie flagella are long whip-like protrusions of the body substance, often ex-
ceeding several times in length that of the body. They are never numerous — one, two,
or four are the most usual, although a larger number is not unknown ; their use, be-
sides projielling the creature through the water, is to assist in the capture of food
particles ; in sedentary species they produce currents in the water, directing them against
the body. In cases where more than one obtains, they are ordinaril}' in pairs, or sepa-
rate and situated at a distance from each other; again, one flagellum, or one set, may
serve to anchor the animal, while another distantly situated may serve for food capture.
Cilia are short prolongations which resemble eye-lashes, hence the name ; it is by their
rhythmical and vigorous lashing of the water that the infusorian swims about so freely,
or, if it is fixed, by the same means water-currents are made to flow past the mouth,
and food is thus secured. The various arrangements of these locomotory hairs will be
given under the description of the order Ciliata, named thus on account of their
characteristic natatory organs. Besides the vibratile cilia, there are other modifications
scarcely to be distinguished from them ; these are setre, or rigid hairs, used for su])iJort,
or for defence ; thick, straight setfe, called stylets, usuallj- situated licneath the body, and
uncini or curved hook-like hairs. The tentacula, in appearance and motion, at first
recall the pseudopodia of some of the Radiolaria, but more careful examination shows
that they are different. Each tentacle is tubular; a structureless external wall termi-
nating in a distal expansion, or sucker, encloses a core of granular semi-fluid matter,
which is an extension of the endoplasm. These organs, situated ]:)romiscuously over
the animalcule's body, on well-defined areas, or on tubercles of the jjeristome border,
may be extended, retracted, or even bent at will.

In the simplest of the Infusoria there is no constant aperture, or mouth, for the
reception of food, but, as in Amoeba, it is passed into the body substance indifferently
at any part of the periphery. It is plain that in such cases a cuticle cannot be
present ; in others a certain definite portion of the surface receives the food. It is
safe to consider such forms more highly develoi)ed. Among those regarded as the
highest of the group, there is a well-defined oral aperture, often reinforced by ap-
pendicular appliances, and from which a passage, the cesophagus, leads into the
endoplasm.

The multiplication of the Infusoria has been studied with much care. It will be
convenient to speak of the several methods : by binary division, by gemmation, by
spores, and by sexual reproduction.

Examples of sub-division are frequently seen, even by the casual observer. The
process was accurately described in essentials by the earliest observers of these animals.
In a majority of instances it takes place across the body; after sejjaration of the
nucleus into two parts, a constriction first appears at the middle, which increases in
depth until the two parts sejjarate, forming two perfectly-formed, free-swimming indi-

30 LOWER INVERTEBRATES.

viduals, and the part without contractile vacuole and mouth soonacquires them. Each
resulting int'usorian, after a longer or shorter time, again divides. Ehrenberg isolated
examples of different species, and after ascertaining how long time was required for
division computed the enormous numbers produced by this process alone. In some
genera, by no means a limited number, the division occurs in the opposite direction, or
longitudmally ; it may not infrequently be seen in Vorticella or Ejnstylis, so that the
large colonies of the latter have thus increased from a single zooid. In certain forms,
at least, the oral aperture, present before di\'ision, is lost, two new ones being formed.
Binary division in a limited number of species, for example Stentor, is oblique.

An instance of multiplication by gemmation is
afforded l.)y Jlemiophrya gefnmipara (Fig. 23). The
buds appear on the anterior border of the parent
animal, tlie nucleus branches, sending out divertic-
ula into the buds. This phenomenon probably
takes place in other species which bud externally.
-,„.,„.,- . .^^ JVbctiluca tniliaris also increases by this process ;

Fig. 23. — Hemiophrifa, (lemmipara, 'With j l j

eight elongate geiumuies, magnified 200 the nucleus first disappears, then the protoplasm

xirii6S<

divides, first into two, then four, and so on. These
masses are at length protruded upon the surface, the flagella are developed, and finally
they are liberated as free-swimming germs.

Sporular multiplication, especially among the Flagellata, has been frequently ob-
served. Tlie careful and patient researches by Messrs. Dallinger and Drysdale have
done much to acquaint us with the phenomena attending this process. In case of the
flagellate monads they found each species to pass through several stages of develop-
ment in their life-history, viz. : the flagellate or mature form, the amoeboid, the encysted,
and the sporular condition ; the last appearing upon the breaking up of the contents of
the cyst. In a flagellate obtained in an infusion of cod-fish it was found that many of
these organisms all at once appeared to jjour out a delicate sarcode, which exhibited
amoeboid movements. Two of these amoeboid masses would unite, after which the
sarcode became spherical, and at length developed the true cystic wall. Upon the
rupture of the cyst, there escaped multitudes of microspores, not large enough to be
individually defined by a magnifying power of fifteen thousand diameters. They were
continuously Avatehed until they developed into the initial forms. Similar phenomena
have been recorded as taking place in the development of the higher Infusoria.

Sexual, or genetic reproduction, in the sense of the union of two distinct and differ-
ent elements, has not been proven to occur. As stated above, individuals entirely
indistinguishable unite before sporular sub-division. It is also well kno-mi that indi-
viduals unite transiently, and then separate to each continue multiplication by binary
division. That the repeated sub-divisions so exhaust the stock that it must necessarily
be revitalized by the conjugation of separate individuals is generally held. It is also
recognized that the nucleus and nucleolus play significant parts in the rejuvenesenee
due to the zygosis, or conjugations. Concerning the interpretation of the facts there
is much difference of opinion. A notice of the several views cannot be introduced here.

O. F. Mtlller, in 1786, first attempted to classify the Infusoria. Eleven of his seven-
teen genera are still recognized in the infusorial class. The number of species included
was about two hundred. Ehrenberg's more elaborate system, published in 183.5, de-
scribed three Iiundred and fifty species (after deducting the rotifers and plants), and
separated them into sixteen families and eighty genera. Von Siebold, in 1845, divided

INFUSORIA. 31

the true infusorial forms into two orders, — Astoma, without oral aperture and Stoma-
toda, with a distinct oral aperture and cesophagus. Claparede and Lacliniann, in 18C8,
for the first time restricted the group to its present limits, and divided it into four orders,
I. Flagellata, II. Cilio-flagellata, III. Suctoria, IV. Ciliata. Stein in his magnificent
work, "Organismus der Infusionsthiere," not yet completed, presented in 1867 the
classification of the Ciliata now generally adopted. The part of the work treating of
the Flagellata appeared in 1878 ; it includes several genera, by many regarded as
undoubted plants — for example, Volvox and Chlamydomonas. The latest proposed
arrangement, by W. Saville Kent, in his Manual of the Infusoria (1880-82), divides
the Legion Infusoria into the following classes : I. Flagellata, II. Ciliata, III. Tenta-
culifera. This author's limitation and arrangement of this group will be adhered to
in the following pages, except that the Infusoria will be regarded as a Class ; hence,
his classes will become Orders and his Orders sub-orders.

Order I. — FLAGELLATA.

The Infusoria of this order bear one, two, or more flagella, which serve them for
locomotion, and assist in obtaining food. They were not unknown to the earliest
observers. In 1696, Mr. John Harris described what is umloubtedly Euglena viridis;
but the modern microscope alone can reveal their organization, and it is in the study of
these lowly organisms that the most substantial progress has been made by recent in-
vestigators in this field of research. Reference may here be made to the discovery of
the collared-monads by H. J. Clark in 1868, and the addition of numerous species to
this list by Stein and Kent, and also to the fact that Stein has found many Flagellata
more highly organized than had been previously supposed. He has shown that many of
the Flagellata possess well developed oral apertures, frequently with the addition of a
pharyngeal dilation, and occasionally a buccal armature similar to that of the Cili.ata.
The flagellum is not the only means of locomotion possessed by some species, like
Ilastigamceba, for these have true pseudopodia like those of Amoeba ; others, again, as
Acti7iomonas, have, besides the flagellum, temporarily developed rays like Actino-
phrys ; a thread-like pedicle is also present in Actinomonas.

Sub-Order I. — Trypanosomata.

The very lowest of the Flagellata now known are two parasitic forms, one of
which ( TryjMnosoma sanguinis) is illustrated by
Fig. 24. The animal is flattened, and has a frill-
like, undulating, lateral border which serves for loco-
motion. It will be seen that one extremity is somewhat
prolonged or attenuate, representing the flagellum ;
the species occurs in the blood of frogs; its congener ^'<*- '^^uaJS'eoS toesT""'"'
inhabits the intestine of domestic poultry.

Sub-Order II. — Rhizo-flagellata.

There occur in pond water, hay-infusions, and the like, some most interesting forms ;
they are so because they have characters in common with the Amoeba; that is, they

32 LOWER INVERTEBRATES.

possess, besides tlie contractile vesicle and nucleus, the ability to protrude the body

substance in the form of pseudopodia, by means of which they progress and take food ;

but they have in addition long vibratile flagella which jilace them in

the higher group, llastigarnceba sitnplex (Fig. 25) serves well to

illustrate this small grou]). A similar form has been often taken by

tlie writer from the soft mud and debris at the bottom of quiet water ;

its movements are comparatively active, and its very long lash is

thrust forward, beating the water with its rapidly vibrating extremity.

Perhaj)s the most remarkable species of the Rhizo-flagellata is Podo-

j^ ■®\ f C^ stoma Jiligermn of Claparede and Lachmann. It is very changeable

S f: -ii :l 'x ''^ shape, and from the extremities of the pseudopodal protuberences

flagella may be produced or withdrawn at will. When these ai"e

not apparent, the animal closely resembles Aniceba radiosa, — indeed.

Fig. 25 — Vasthiam- lilitschli has recently attempted to show that it is the same species ;

iarged no'times" ^^^^' °" *^® Other hand, it has been pointed out that the feet of Amoeba

radiosa, however attenuate, are never thrown into spirals, nor vibrate,

as in Podostoma. It should be looked for in infusions of hay.

Sub-Oedek III. — Radio-flagellata.

The Radio-flagellata, which follow very naturally the forms last mentioned, are
mostly marine. They may be compared to the Radiolaria, which they resemble very
closely in their ray-like j^seudopodia, but, in addition, they are j^rovided with one or
more lashes. Again, some of them are naked, while others are provided with silicious
cases or loricie. It should be remembered that these genera with tests are included by
Haeckel in tlie Radiolaria. Is the possession of flagella a sufiicient distinction for thus
removing these to the Flagellate Infusoria ? Without considering the intermediate char-
acter oi Acti)iomonas snA Actinolophus j^edunadatzis, it would seem not; but these
forms bridge the chasm as well as that between the Rhizopoda and Rhizo-flagellata is
bridged.

A characteristic example of the sub-order is Actinomonas mirabiUs. Its body is
globular, sujjported on a thread-like stalk several times longer than the diameter of its
body; from every part of the periphery radiate sarcode rays in search of food ; at the
top extends a long flagellura which, by its motion, causes water-currents to pass over the
rays. Food particles are taken, indifferently, at any part of the surface.

Stjb-Oeder IV. — Pantostomata.

We have now to consider true infusorian types where the injestive area is dif-
fuse, as in the preceding sub-orders, but which lack the pseudopodal appendages which
allied those groups so closely to the Rhizopoda. This extensive sub-order includes
eighteen families, divided into three groups ; viz. Monomastiga with one flagellum,
Dimastiga with two, and Polymastiga with three or more.

Every one who has used the microscope with any considerable magnifying power in
the examination of infusions, or the water of ponds, has doubtless seen minute globose
or elongate plastic bodies moving about l»y means of a single long thread placed at one
end of the body. These forms belong to the genus Monas. As now limited, the
family Monadid^, includes only the naked free-swimming species with one flagellum.

INFUSORIA.

33

The earlier writers were in the habit of dcscribiug any flagellate, just discernible with
their lenses, as Jlonas, no matter how many flagella it possessed, hence the nimiber of
so-called si3ecies of Monas is very large. Many have been put into other genera, while
others are still doubtful. It was one of these, Monas dallingeri, that served for the
beautiful series of observations on the life-history of the monads referred to on a jsre-
vious page. These minute creatures can be studied only by means of high powers. If,
after long and careful watching, a form is found, otherwise just like Monas, which does
not change its shape, it belongs to Stein's genus Scytomonas ; if the anterior border is
truncate it is Cyathomonas ; fusiform and persistent in shape, Leptomonas ; vermicu-
lar and spirally twisted with form persistent, Ojyhidomonas ; vermicular and change-
able in form, Herpetomonas ; if adherent at will by a trailing flagellum, Ancyromonas.
This analysis is given to show with what care these animals must be studied before they
can be properly referred to their genera.

The remaining three families of the Monomastiga differ in having the flagella lateral,
or the animalcule with a tail-like filament, or enclosed in an indurated sheath, the lorica.
In the genus Socio, the ovoid, or elongate, plastic bodies have a tail-like filament ; they

Fig. 26. — Five zooids of Anthopht/sa^ enlarged 1000 times.

Fig. 27. — Large colony of Anthophyscu

are mostly parasites in the intestinal canal of animals, especially of reptiles and insects.
At times they abound in myriads. The encystment of £. lymnmi has been recorded
by Ecker. On examining the opaque eggs of the pond-snail, many were found densely
packed with minute cysts ; these bursting, gave birth to swai'ms of monadiform germs.
The two most remarkable and beautiful genera are loricated. Codoiueca costata, an
American salt-water form, was described by H. J. Clark : the bell-shaped lorica or case
stands erect on a rather long, rigid stalk ; the upper pai't of the cup is expanded and
ajjparently fluted. Kent has discovered another species with a smooth, ovoid lorica; it
inhabits pond-water. The other loricated form, Platytlieca micropora, differs fi-om the
preceding in lying flat upon its support like Platycola of the peritrichous Ciliata ; it is
found on tlie roots of the duck-weed.

The first family of the Dimastiga includes singularly striking species, which, by theh-
tree-like supports, or zoodendria, may easily be mistaken for an Epistylis ; in fact,
more than one of the few species have been figured and described as species of the
genus named, but the irregular, oblique animalcules bearing two, equal, anteriorly
placed flagella should at once determine the proper jjlace of these forms. The writer
once found an Anthophysa abundant in a jar of water in which Chara fragilis had
been kept for some time ; it was taken for A. vegetans. Colonies attacTied to their
granular, fragile stalks were seen, but the greater number were free-swimming. Figs.

VOL. I. —3

34

LOWER INVERTEBRATES.

Fig. 28. — Ideal section of a colony of Anthophtjsa.

26-28 illustrate a species which the unequal flagella and oblique anterior border
of the zooids appear to place in the genus A)Uhophi/sa. It was discovered in Spy-
Pond, Cambridge, Mass., by A. H. Tuttle, who gave an account of it. He fed the
monads indigo, which they took readily. When a particle was taken, the longer flagel-

lum, which did not vibrate (the short
one was in constant motion), was
suddenly turned down, carrying the
food with it into the oral region.
The number of individuals in a
grouj) varied from a few to many,
giving the larger colonies a mul-
berry appearance. Fig. 26 repre-
sents a group of five zooids attached
by their bases. Fig. 28 is an ideal
section showing the outline of the
zooids and their manner of attach-
ment to a common pedicle, the
upper part of which alone remains,
the colony liaving broken away from
its anchorage. Kent has recorded the manner of growth of the pedicle in this genus. A
colony were fed with pulverized carmine, which they ingested greedily, but it was soon
rejected. This was effected entirely at tlic posterior extremity or point of union with the
stalk, which was soon changed in appearance and dimensions, for the rejected particles
of carmine were utilized in increasing it ; the amber color and striated aspect gave
place to that due to tlie agglutinated opaque carmine. The growth was so rapid that
in one group the j^edicle nearly doubled its length in half an hour.

Among the most graceful forms of this sub-order the species of Bicosceca must cer-
tainly be enumerated. They occur in both salt and fresh-water; the globose, urceolate,
or ovate loricfe are usually stalked, while the contained zooids also are pedicellate, the
usual two anterior flagella are unequal. But for the lashes it would be easy to mistake
these creatures for a loricate peritrichous ciliate like Cothurnia. There are also in this
assemblage several endoparasitic species, — • for example, Pseudospora vohocis, which
resides in Volvox fjlobatoi; where it eats up the cell contents ; it is figured with a
number of pseudojjodia, thus recalHng 3Iastigamoeha simplex. Another example is
Lophomonas hlattarum, which, as its name implies, inhabits the intestinal canal of the
cockroach (Blatta); it is a plastic form with a tuft of flagella anteriorly. Another para-
site, Hexamitra intestinalis, occurs in the digestive tract of Triton ; it has six flagella,
four anteriorly and two posteriorly. It swims free or anchors itself by means of its
posterior lashes ; when in this position it swims about or gyrates from right to left, —
twisting the threads into one, and then, reversing its motion, winds them in the opposite
dkection.

Sub-Okdek V. — Choano-flagellata.

This sub-order includes only three families and seven genera. The characteristics
of these remarkable Infusoria were first made known through the researches of H. J.
Clark in 1868. It is a matter for pride that this honor should fall to an American.
A type of these forms is represented in Codosiffa hotrytis (Fig. 29), with which the
other species may be compared. The animals of the family to which this species

INFUSORIA.

35

belongs are naked ; those of Codosiga and Monosiga are attached, while tliose of
Astrosiga and Desnmrclla are free-swimming. Those of the second family are loricate ;
Salpingceca and Laganasca are solitary, the one sedentary, the other free, while the
animals of the reraaming genus, Polymca^ are united, forming branched sujjports.
The third family has the animalcules united by a gelatinous matter into colonies ; the
two genera are Phalansterium, Avith the collar rudimentary, and Protospongia., collar
well developed.

The form represented in Fig. 29 will at once be seen to belong to Codosiga, for
the zooids are naked, stalked, and united
socially. The leading peculiarity upon
which the sub-order is founded is the
hyaline, wine-glass shaped collar, borne
at the upper, or anterior extremity of the
body. In the centre of this cup arises the
single flagellum, which by its motion
about the cup causes currents of water
to pass in on one side, down to the bot-
tom, and out on the other side ; the discal
area at the bottom of the collar receives
the food ; waste particles are also rejected
at this point. The collar may be with-
drawn into the body, and again protruded
at will. Codosiga botrgtis appears to
have been described by Ehi-enberg, under
the genus PJpistglis of tlie peritrichous
Ciliata. According to Kent it is Codo-
siga pulcherrhna of Clark. They in-
crease by binary division, as shown in
Fig. 30. C. botrgtis hSs also been ob-
served to withdraw its collar and flagel-
lum, and protrude rod-like pseudopodia
from its surface, after which a cyst formed
over the body contents, the latter ulti-
mately breaking up into sporular bodies.
Tlie pseudopodal spines sometimes occur
before the disappearance of the collar.
This cosmopolitan species should be
looked for on aquatic plants. Mono-
siga steinii is not uncommon on the stems of Ejnstglis jMcatilis. When one of the
pedicles containing them is examined witli a magnifying power of six hundred diameters
or upwards, the minute, solitary, sessile zooids of 31. steinii may be seen to good advan-
tage. One other genus of the group can alone be mentioned ; it is Salpingrpca, of whicli
there are nearly tliirty species known. The animals are, if possible, more beautiful tlian
those already mentioned ; for they liave, in addition to the graceful outline of the zooid,
an equally graceful lorica. ^S". amphoridium, described by Clark, has a very wide
distribution; it abounds on confervas, the sessile lorica often incrusting tlie plants.
They have been seen to divide, the separated portion moving away by means of pseu-
podia ; in this condition it has the appearance of Amoeha radiosa. After a time it

Fig. 29. — Codosiga botrytis, greatly enlarged.

36

L 0 WE It IN VER TEBRA TES.

secretes a lorica of the pristine beauty of its species, soon acquires a collar and flagellum,
and is lienceforth indistinguishable from its mature kindred. In the
recentlj' described SjMngomonas haeckeli, Ave are made acquainted with
a most remarkable infusorian, — one which, if it fulfils the expectation
of the discoverer, Mr. Kent, will jirove of unusual interest to a large
number of students in zoology, and its dedication to Prof. Haeckel
particularly apt. The zooids differ from the preceding only in being
more plastic, the collar and flagellum being suddenly withdrawn on the
least disturbance, the body then taking on an amceboid aspect. The
animals secrete a mucilaginous stratum in \\'hich they dwell, studding
its surface when expanded. Should this disposition of the zooids take
place in " sacular invaginations of this matrix, it would produce what
would have to be accepted as an undoubted, though very rudimentary,

Fig. 30. — Fission onono-p-stock "
In Codosiga. SpODge-SlOCK.

StXB-OkDER VI. — EUSTOMATA.

The Eustomata differ from the forms previously described, inasmuch as they
have a definite oral aperture, instead of ingesting their food at any part of their sur-
face, or, as in the collared monads, only at a disc bordered by the collar ; they differ
also in having the outer part of their bodies much firmer than the endosarc, hence
they are as a rule less plastic, and m a few instances the outer layer is indurated after
the manner of some of the higher Ciliata. They never have more than two flagella, so
they are separated into groups of families, accordmg as the zooids have one or two
flagella. The forty-si.x genera are distributed among eleven families; there are in-
cluded many forms well-known to observers of pond-life.

In the first family (Astasid^) the monads are free, constant in form, colorless, the
generic differences being found in the shape of the body, — ovate, flattened, flask-shaped,
etc. ; it includes Astasia with a distinct tubular pharynx, and ColiJodella without it.
Astasia trichophora is frequently met with in marsh-water. Although its forms are
protean, perhaps its more usual attitude is ]iyriform ; from the narrower anterior end
issues a cord-Hke flagellum, mistaken by Ehrenberg for a neck like that of Trachelocera
olor (Fig. 39). The ingestive orifice "consists of a large, widely dilatable, but simple,
aperture, continued backwards into a clearly-defined jiharyngeal tract." This structural
character marks a broad distinction between this genus and Euglena. Biltschli has
shown that the contractile vacuole of ^4. trichophora by its contraction forces a part
of its contents out into lateral canals in a manner snnilar to that in
Paramecium, and others of the Ciliata, to be described further on.
The second family comjirises forms highly changeable in outline, and
colorless.

The EuGLENiDJE differs from the Astasidoe in having the endoplasm

brilliant green, and in having an ingestive apparatus capable of taking

,,j ,, jt only minute particles. Euglena viridis is known by, or has been seen

U\.Jj/^ by, every tyro with the microscope. Its developmental forms are so

T-wvT" -\arious that it has been described under many names. Stein has ob-

serA-ed a division of the nucleus to take ijlace ; the separate masses in

Fig. 31.— 7'racAf/- ' t , • i,

omouas inspida, some mstanccs acquire an ovate outline, surrounding themselves with
times. a dense coat, while others become thin-walled sacks, full of minute gran-

INFUSORIA. 37

ales, each of which is jsrovided witli a single cilium. Tlie loricated form, otlierwise
agreeing with Euglena, is Trachelomonas, common in ponds and bog-water. Asco-
glena differs from the last in being sedentary ; from this Colacium differs in the absence
of the sheath, and in having a branching pedicle.

The phosphorescent Noctilucid^ embraces the genera Nbctiluca and L<;ptodiscus.
N. miliaris (Fig. 3^) is a large form, visible to the naked eye, found in immense imm-
bers in the superficial waters of the ocean, and it is one of the
causes of their pliosphorescence. It is colorless, spherical, with
a meridional groove on one side, at one end of which the mouth
is situated. A long, slender, transversely striated tentacle over-
hangs the mouth, on one side of which a hard, toothed ridge
projects; close to one end of this is a vibratile cilium. The
protoplasm consists of a central mass, with radiating portions

. . .,, , -,1 . ■I' , FiG.32. — JVorii(»ca jKJ/jam.

connecting it with the sub-cuticular layer ; there is a tunnel-

shajied depression leading into the vacuoled central mass, through which the food passes
into tlie same. The phosphorescence appears to emanate from the layer just under the
cuticle ; for it has been observed that as the light gradually fades away on the death of
the animal, as when one has been immersed in alchol, that the light finally ajipears in a
ring around the body, since the observer is looking down ujion a thin splierieal film of
light, imperceptible in the single layer over the middle of the globule ; but at the borders,
where seen as if on edge, sufficient light is sent forth to make it visible. When disturbed
they become more highly luminous, so that a fish, for example, moving through the water
where they are abundant shows its luminous sides, and its course is marked out by a
path of emerald green light. Tliis form is comparatively common in Eurojjean seas,
but has only been found, so far as we are aware, by Mr. C. B. Fuller at Portland,
Maine, and by Prof. Hyatt and Mr. Kingsley at Annisquam, Mass.

Among the second division of this sub-order — viz. mouth-bearing, two flagellate forms
— are many interesting and well-known species. The Entomostraca, especially those in
puddles of the forest in sjiring time, are often loaded down with a green, oval form,
which stands singly, or in groups, on short pedicles. On superficial examination it would
be easy to mistake it for a Colacium; but on account of its two flagella during the
motile period, its firmer cuticle and its two lateral pigment bands, it has been separated
from Colacium. as Ghlorangium stentoriuuni. Whether the flagella remain during the
sedentary stage or not has not been determined. In Uvella the animalcules are in
colonies, free-swimming, and the flagella are sub-equal.

Two loricated genera, Epij^yxis and Dinohryon, are unsurpassed in beauty by any
of their kindred. The lashes are unequal, and the animal is attached to its vase-shaped
lorica by a posterior, contractile fibre ; the individuals of Epipyxis are sessile upon
eonfervse, while those of Dinobryon occur in branching chains of lorica i. e. each
individual set free by sub-division is attached to the inner margin of the case of the
parent. In early summer a species, presumed to be D. sertularia, abounds in the water-
supplies of cities along the Great Lakes.

StJB-OrDER VII. — CiLIO-FLAGELLATA.

The animalcules of the Cilio-flagellata have one or more lash-like flagella, and, in addi-
tion, a more or less highly-developed ciliary system, thus indicating a position between
the Flagellata proper and the true Ciliata. At first only the Peridinidse were included,

38

LOWER INVERTEBRATES.

Fig. 33. — Cilio-flagell;ite, en-
cysted, enlarged 300 times.

but recent investigations have considerably enlarged its borders. It now embraces five
families, the typical forms being included in the PEPaDiNiDj;. These are free-swim-
ming animalcules, sometimes naked, but in most cases the body is enclosed in a hard
case, A'ariously ornamented, the angles sometimes being prolonged into long spines.
The case or cuirass has recently been proved to be cellulose, a substance hitherto only
known in the Ascidiaiis, outside of the vegetable kingdom. The cilia occur as a central
or eccentric girdle, more or less complete ; in the cuirassed forms the shell is usually
divided by a groove, the borders of which are ciliated. The shell is either composed
of one uniform piece or is made up of plates. There arise from some parts of the body
one or more flagella. In life these flagella are seen to suddenly disappear, and a close
examination has shown (in Ceratium) that there is a small cavity situated at the base
of the flagellum into wliich that organ retreats, bringing with it foreign bodies which
serve for food. Tlie nucleus is usually spherical or oval,
while a contractile vacuole is occasionally found. They are,
like JSToctiluca, highly j)hosphorescent. They have been ob-
served to become encysted, when segmentation, on a more
or less extensive scale, occurs. In some cases the cyst is en-
closed in the carapax ; in other instances the cuirass is thrown
off, and a new cyst of a different form is secreted, which often
has one or both extremities prolonged into attenuate curved
horns, giving it a crescent shape (Fig. 33), resembling certain desmids ( Closteria). They
sometimes hibernate in this condition. They occur in both salt and fresh water.

Of the ten genera of the Peridinidaj the species of three are naked, that is, resemble
in essentials those of the loricate forms which have thrown off the
case previous to cncystment. Gymnodinium puhiscidus is, per-
haps, as often met with as any; it occurs among Algre in pools,
often in great numbers, is somewhat spherical, with a transverse
groove, and is brown or yellow in color. The best-known genera
are Glenodinium, and Peridinium without horn-like processes, and
Ceratium, with conspicuous processes on the
shells. G. cinctum is well known to observers
of pond-life ; its smooth case should distinguish it
from a s'lmUnr I^ericlifimm with faceted carapax.
These genera are represented by several species in American waters.
Mr. H. J. Carter has described a most remarkable instance of the
coloring red of the waters around the shores of the Island of Bom-
bay by P. sanguinea. During its active stages this species is green
and translucent ; gradually, as the time approaches for it to assume
its quiescent or encysted state, refractive oil globules aiijiear within
the interior, and the green gives jjlaee to red, and thus the water
containing them acquires a deep vermilion hue. It is probable
that other instances of red waters are due to similar causes. The
characteristic Ceratium (Fig. 35) aj)pears to be a cosmopolitan
infusorian. It has been knowii a long time as C. longicorne, but
R. S. Berg has recently indentified it with Bursaria hirundinella
Fia.i5.- Ceratium hirim- of O. F. Muller, which, if Correct, will chanw the specific name to

dmella, enlarged 300 ' ' t r ■ ,

times. the one having priority. C. hirundinella occurs often in large

numbers in the water-supply of all the cities along the Great Lakes. It is most abun-

FiG. 34. — Giimnodin-
niin lackmannii
dividing, greatly
enlarged.

INFUSORIA.

39

dant in the fall. It may be said always to occur in these localities, together
with a rotifer, Anuraa longispina, which has singularly long anterior and
posterior spines corresponding in number -wdth those of the infusorian.
The resemblance is striking. Mr. J. Levic has recently found the same
forms together in Olton Reservoir, near Birmingham, England.

The species of the remaining families have one or more flagella (usu-
ally one), with the body more or less clothed with cilia; in some the
whole surface bears them, in others only a crown of cilia occurs at the
anterior end, the flagellum standing in the midst. Asthmatos ciliaris
(Fig. 36) exemplifies this structural peculiarity. This species occurs in the
mucus from the nasal passages of persons suffering from " hay fever," and
is held by Dr. J. H. Salisbury to be the cause of this distressing complaint.

Fig. 36. - Aslh-
viatos ciliaris,
magnified 500
times.

Order II. — CILIATA.

The animalcules of this great order, as the name implies, possess cilia as locoraotory
organs. They are much more highly organized than the Flagellata, and many of the
forms included are generally better known, and are more
generally called to mind by the name Infusoria. Stein's
division of the order into suborders is as follows: Holo-
tricha, with cilia over the whole surface ; Ileterotricha, with
cilia distributed over the entire surface, having those near
or surrounding the mouth longer; Peritricha, cilia mostly in
a wreath about the mouth ; and Hypotricha, with cilia on
the ventral surface only.

Sub-Order I. — Holotricha.

A common type of the first sub-order and of the family
Paramecid^ is Paramecium aurelia (Fig. 37). It occurs
in hosts in vegetable infusions, stagnant pond-water, etc.
These active, elongate, animalcules are alike the delight of
the amateur microscopist and the joy of the veteran inves-
tigator ; it is to him wh.at the frog is to the general anato-
mist and physiologist. It was made for investigation ; the
comparatively large size and transparent body fit it admir.al )ly
for study, and it has not been neglected. The anterior third
of the body is somewhat flattened and twisted, so that the
flattened face resembles a living figure of 8 ; near the middle
of the ventral face — at the posterior extremity of the 8 —
the mouth is situated. The rejectamenta issue at a j)oint
about half-way from the oral aperture to the posterior ex-
tremity of the body. There are two contractile vacuoles near
the extremities. When expanded they are round, but when
contraction takes place there appear fine radiating streaks,
which, as the main portion decreases, gradually broaden,
until, when the former is nearly invisible, they are extended
over half the length of the body. It has been suggested

■\-— I.

:_.J_t_ m.

c.

Fig. 37. — Paramecium aurelia^
greatly enlarged, b, c. Con-
tractile vacuoles, tf. Mouth,
e. CEsophagus. g, i. Food vac-
uoles, h. Nucleus, m. Kndo-
sarc.

40 LOWER INVERTEBRATES.

that these phenomena are really due to abnormal pressure of the cover glass. Para-
mecia increase by transverse fission. The cortical layer contains numerous vertically
disposed rod-like bodies called trichocysts. When a Paramecium is treated with very
dilute acetic acid these protrude from all parts of the surface, giving the animal the
appearance of being clothed with very long cilia. A solution of tannin in glycerine pro-
duces a similar effect, although it is claimed by a writer in the Journal of the Royal
Microscopical Society that it is due to a hardening of the cilia. These trichocysts
have various forms and dispositions in different species. Some regard them as ho-
mologous with t''-C thread-cells of the CVelenterata, and as having a similar function ;
others regard them as tactile organs. Biltschli has described a species, Polykrikos
schicartsii, which has trichocysts entirely similar to the thread-cells of
the sea-anemone. Since this infusorian inhabits salt-water, and the
trichocysts are irregularly disposed, Kent suggests that they may be
thread-cells which have been swallowed. Paramecium bursaria (Fig.
38) is shorter and broader than P. aurelia, and is less flattened ; the
buccal fossa is funnel-shaped, extending oblicpiely from left to right.
The nucleus is oval and the nucleolus is attached to the side of it.
P. bursaria is usually colored green by chlorophyll granules, — now
held Ijy some to be parasitic algte, as is also the green color of the fresh-
FiG. 38. — /'arame- -^pater sijonges, and the common green Hydra. Owing to the presence
magnifled 250 ^f ^jj^^ green corpuscles the cu'culation of the endoplasm is seen to
better advantage than, perhaps, in any other infusorian, although there
are forms like Vbrticellce which exhibit this phenomenon in a marked degree. Tliis
rotation is uniform, ascending on the left side, and descending on the right, when seen
fi'om above (indicated in the figure by the arrows). Balbiani has shown that the so-
called longitudinal fission is not really a fission, but a phase of the act of conjugation.
Two animalcules may remain attached by their anterior extremities for several days;
after separation, the nucleus and nucleolus changes, the latter becoming more or less
striated, while the former breaks uj) into a variable number of sjjlieroidal bodies, which
finally separate from the parent, and possibly are to be considered as ovules.

Among the most curious of cihate Infusoria those of the family Tracheloceeid^
are entitled to the front rank. Their flask-shaped bodies are drawn out anteriorly into

a long flexible neck, with the oral
aperture at its terminus. Trache-
locera olor (Fig. 89) is the type of the
'^^|>-^ group ; it appears to be cosmopoUtan,

Fig. 39. — TVacfe/ocera oZoi-, enlarged 375 times, c. Contractile occurring among algffi in ponds and

vesicle, m. Moutli. n. Nucleus. . .

Streams. Under examination in the
living state it appears to be incessantly exploring for food, thrusting its wonderfully ex-
tensile neck right and left into every cranny. As it swims gracefully through the water,
with a spu-al motion, its form and attitude very naturally suggest the swan. In Lachry-
maria the neck is only slightly extensible. Ifaryna socialis, as its name implies, affords
an instance somewhat rare among the Holotricha, that is, the formation of a zoocytium.
This structure is branched like a tree, the cup-shaped zooids projecting from the termina-
tion of the branches. Amphileptus gigas is an elongate compressed animal, which may
easily be mistaken for a Trachelocera on account of its long neck, which assumes as
many shapes as in that genus ; it is readily distinguished, however, since the mouth in
Amphileptus is at the base rather than at the apex of the proboscis. It is said to feed

INFUSORIA.

41

on animalcules, ■which it takes by means of its trunk, transferring them to its mouth,
after the elephant's manner of feeding. It has a number of contractile vacuoles, from
ten to fifty, arranged in two longitudinal rows, as mentioned on a previous page. It
is one of the largest known Infusoria.

The next family (Teichontjcphid-e) is characterized by the possession of a mem-
braniform expansion as well as cilia. The type may be illustrated by the interesting
Trychonympha agilis (Figs. 40 and 41), described by Leidy as parasitic in the digest-
ive canal of the white ant, Tennes flavipes. He observed that the canal was dis-
tended by brown matter, which on examination proved to consist largely of infusorial

Figs. 40 and 41. — Trichonymplia agilis, enlarged 450 times, n. Nucleus, i. Ingested food particles.

jjarasites and particles of wood. Three sjiecies, belonging to as many genera, were dis-
covered. Fig. 40 re23resents T. agilis in its extended position. As it 2)rogresses in its
medium it takes on many protean forms. The cilia are arranged apjDarently in series,
some longer than others. The oral aperture is terminal. Until its life-history shall
have been made out, its place in the system and its relation to its companions are
uncertain.

The mouthless Holotricha (Opalixid.e) are all 2Darasitic, degraded forms. They
have been taken for the larvae of JDistomce. These now unquestioned Infusoria should
be looked for in the intestines of frogs, moUusks, and worms. Opalina and Anoplo-
phrya are examples.

Sub-Order II. — Hetebotricha.

As was mentioned on preceding page, the Heterotricha are chai-acterized by the
possession of cilia on the whole surface, those surrounding the mouth being longer
than those on other portions of the body. In all except Bursaria and its allies the
above definition holds good ; there the oral cilia do not encircle the mouth. With
the mention of these exceptions, we may now pass to a consideration of a few of
the typical forms.

In Spirostomum ai"e met Infusoria which at once arrest the attention, both by their
elongate, snake-like form and theii- remarkable anatomy. Spirostomum ambiguum
(Fig. 22) may serve to illustrate their striking features. The figure represents the

42

LOWER INVER TEBRA TES.

animal somewhat contracted. It is capable of gi-eat distention, so as to become fifteen
or twenty times longer than broad ; it then attains a length of one-twelfth of an inch,
or even more. Its cylindrical body, sometimes flattened, is rounded at the extremities,
often truncate posteriorly. The single line of peristomal hairs extends down the
left side of the anterior ventral face to the oral aperture, situated near the middle of
the body. The remarkable contractile vesicle and nucleus have been referred to al-
ready. The generic name was given on account of the apparently spiral peristome, as
seen when the animal twists itself about its long axis. The writer recently found this

species so abundant on a scarcely submerged moss
that the water taken up by a dipping-bottle was
rendered turbid by them. The solution of tannin
in glycerine, previously referred to, appears to be
a valuable reagent for studying this animalcule.

The Stentors, or trumpet animalcules, are
among the most entertaining heterotrichous In-
fusoria. They are large, active, and often highly
colored, so that a colony of them incessantly ex-
tending and retracting their bodies, at the same
time driving, by means of their oral cilia, strong
currents of water against their peristomial sur-
faces, presents a scene, when well defined by the
microscope, not soon to be forgotten. The ex-
cellent cut (Fig. 42) of Stentor pohjmorphus^ a
widely-distributed form, displays the characteris-
tics of the genus far better than words can do.
The Stentors often secrete gelatinous sheaths,
which sometimes embrace several individuals.

This group has, too, its species which secrete
a lorica, and as in other cases they are very attrac-
tive objects. An example may be cited in Fol-
liculina : its flask-shaped sheath is attached by
the side, the neck being bent upwards. The
animal closely resembles a Stentor, except that
the peristome is two-lobed, instead of nearly cir-
cular. The species are defined according to the
shape of these lobes. FoUicidina ampulla has
been found in America by Dr. Leidy. In Clmtoqnra the two lobes give place to
a slender ribbon-like extension of the anterior region, which, when extended, is twisted
into a spire ; a hyaline expansion also extends laterally along the broad part of the
peristome, giving the extended zooid a unique ajipearance. It is not attached to its
surrounding sheath. The preceding loricate forms are sedentary ; on the other hand,
Tintinnus includes free-swimming sjiccies. The beautiful tests of these are common
in the water-supplies of most American cities.

In the genus Codonella there are an outer circle of twenty tentacle-like cilia, and an
inner one of lajipet-lUve appendages ; the case is similar to that of the preceding.

Fig. 42. — Stentor poh/morphus. n. Nucleus.
cv. CoutractUe vacuole. Magniiied 90 times.

INFUSORIA. 43

Stjb-Oeder III. — Peritkicha.

This group resembles the preceding, and indeed there are a few forms whose exact
position is doubtful. The typical Peritricha, however, have the cilia confined to a circle
around the mouth, while it is only in the aberrant forms that sujiplcmentary cilia are
found. The members of the sub-order are divided into two not very natural divisions,
according as they are free or attached, at least during a portion of the e.xistence of the
individual. The attached forms frequently develop elegant cases, or in other instances
beautiful branching colonies.

As an example of the first (free) group v:e may consider the unusually active Hal-
terice, which are globose forms seen in water from ponds, especially after it has been
standing for some days. They have a spiral ador.al wreath of cilia for swimming, and
usually, in addition, a girdle of long-springing seta?, by me.ans of which they leapi com-
paratively long distances. One may be quite under the observer's eye, when to his an-
noyance instantly it darts out of the field of view. To facilitate their study Clajiarfede
and Lachmann recommended placing under the cover
with them a form like Acineta. They soon jump
against its sucking tentacles, where they stick fast,
and then may be conveniently examined. Fig. 43
illustrates Halteria volvox. It resembles the more
common JI. grandinella in form and in leaping or-
gans, but has besides an equatorial zone of long, re-
curved cilia. A singularly aberrant form ajjpears in
Torquatella tunica, described by E. Ray Lankester. fig. 43. — //a»cr;«ro(TO;r, greatly enlarged.

^ . , . , n. Nucleus, cd. Contractile vacuole.

Around the front margni there is a membranous ex-
pansible frill, which is jilaited, and alternately closes up and expands with a twisting
motion. It was obtained in salt-water from decaying eggs of the worm Terehella.

Any one having examined the common Hydra, or the gills of Nectv/rus lateralis to
any extent with the microscope has doubtless encountered minute bodies gliding over
the surface of the hosts, or now and then swimming rapidly away, but soon returning.
Seen from above they are discs ; from the side, shaped like a dice-box. Prof. H. J.
Clark studied carefully their anatomy. He showed that the body surface between the
concave extremities is ribbed by the thickenings of the body walls ; that the posterior
truncated margin produces a thin annular membrane called the " velum," mto the base
of which, and on its inner side, the posterior fringe is inserted ; that the nucleus, ex-
amined in the fall, was a moniliform, band-like spiral situated near the truncated base.
Besides the vibratile cilia of the border of the posterior disc, there is on its inner border
a WTeath of stout hairs or uncini, in an outer and an inner series ; those of the outer
circle are stout and curved, the others, slender, straight, and appai-ently radiating from
the centre of the discal area ; they consist of a solid portion and a membrane-like
expansion. These forms belong to the genus Trichodina.

The family Voeticbllid.s; includes the attached forms of Peritricha. The three
sub-families are Vorticellina^ (naked), Vnginicolina^ (loricate), and Oithrydina; (in gela-
tinous covering). The student of protozoic life must ever find the keenest delight in the
study of this varied family, examples of which may be found at any time of the year, or
at any jilace where there are natural or artificial bodies of water. In Vorticella, the
type of the family, each individual is solitary, and consists of an oval body attached by a

44

LOWER INVERTEBRATES.

slender stalk to some foreign support. At the end of the body farthest from the sup-
port, a band of cilia surrounds a flattened disc, at one side of which is the opening
dignified by the name of mouth. On careful e.Yamination it is seen that the band of
cilia does not form a complete cn-cle, but rather a spiral, the inner end of which passes
into the mouth and down the tube known as the oesophagus. The nucleus is sausage-
shaped, and in many forms is coiled in a spiral. The
stalk is also an interesting portion of the anatomy, as
witliin the external cuticle one may by careful examin-
ation see a core of contractile protoplasm, whose func-
tion will apjiear further on.

Since Vorticella is one of the most common of the
Infusoria, it may be well to give here a slight account
of its method of life, as illustrative of the physiology of
the whole class. On placing a little powdered carmine
in the water in which the Vorticellce are living, and ex-
amining them under the microscope, it will be seen that
the motion of the cilia around the mouth creates a cur-
rent of water, which pursues a constant direction down
the oesophagus and then out again. The particles of
carmine and other small bodies in the water follow the
general course of the current down to the bottom of the
oesophagus but are not allowed to go out again. In this
way a ball of nutritious matter is formed, which soon
forces its way into the protoplasm of the body, where it
is known as a food vacuole. These food vacuoles keep
/.-. Ectosarc. xvp a Constant though slow motion through the body,
passing down on one side and up on the other, vmtil at
last all nutritious substance is digested, when the rejectamenta are forced out into the
beginning of the oesophagus and carried away from the body by the outgoing current
of water.

It requires considerable time and much patient watching to make out these points
in Vbrticella, for though attached, these animals are far from stationary; every few mo-
ments the cilia will be suddenly withdrawn, and the animalcule will itself as suddenly dis- ■
appear. On moving the slide one readily ascertains the cause of this, for it will be seen
that the contractile protoplasm of the stem has exerted its powers, and the long, slender
stalk is now coiled in a close spiral. Gradually the stalk straightens out, when the
contractile vacuole renews its pulsations, and the cilia begin their vibration as suddenly
as they had stopped them a minute before.

The process of binary division in these familiar objects is of high interest ; it is
longitudinal; first the ciliary disc is withdrawn, and the body assumes a spherical con-
tour ; it soon becomes dilated, and a notch appears in the anterior border ; a new
vestibular cleft and oral system is developed on each side of the median line ; a line of
division now proceeds from the anterior notch, through the centre of the animal's body,
cleaving both the contractile vesicle and nucleus. The result is two animalcules on a
single stalk. One zooid remains attached to the original pedicle, the other, with its
peristome usually contracted, develops round the posterior region of the body a circle of
cilia, by the action of which its attachment to the pedicle is broken, and it swims away^
soon to attach itself and acquire a new stalk. Then the temporary girdle of cilia is

Fig, 44. — Vorticella nebulifera, enlarged
about 600 times, a. Cilia, b. Cili-
ated disc. c. Peristome. (/. Vesti-
bule, e. Gl]sophagus. /. Contractile
vacuole, g. Food vacuoles. A. Nu-
cleus, t. Endosarc.
vu Muscle of stem.

INFUSORIA. 46

absorbed, the peristome border is now displayed, and the lousiness of adult life com-
menced. Another sort of sub-division has been recorded by Stein, and confirmed by
others. The body divides into two unequal parts, after which the lesser one is set free,
and then enters into genetic union with some other normal Vorticella. This union is
supposed to produce a rejuvenescence, which means a capacity to continue the pro-
cess of multiplication by self-division. That the union is followed as in the Flagellata,
by encystment and sporular sub-division, has not been demonstrated. Perhaps this
word of caution is necessary ; the individual VorticeUa may often be seen with the
posterior ciliary wreath. This is not always an indication of recent division, for
when these animals become dissatisfied with their surroundings they produce the
extra cilia, and remove from the old pedicle, and set up in a more congenial place.

Among the forms allied to Vorticella we may notice that in Spirochonia the attach-
ment is by means of a disc, and the peristome is developed into a hyaline, spirally con-
volute membranous funnel. Stijlonichia is similar, except that the body is mounted
on a rigid pedicle ; in Hhabdostjla the body is like that of Vorticella^ but the jjedicle
is not contractile, but flexible. In Carchesium the zooids are united in social tree-
like clusters, but the muscle of the pedicle does not extend through the main trunk;
the individuals can withdraw themselves to the point of branching of their stalk, but
the colony cannot withdraw itself from its position. In Zoothamniimi, on the other
hand, the muscle is continuous throughout the colony. In this genus there are
zooids of more than one form and size in the same colony. In the genus JEj^istylis the
branched pedicle is rigid throughout, the base of the body alone being contractile.
Members of this genus are, doutless, next to those of Vorticella, most frequently met
with. Their tree-like colonies are readily seen by a hand lens on aquatic plants. The
carajiax and gill chambers of the cray-fish, and the shells of aquatic snails, are also rich
hunting grounds for these creatures. Opercularia differs from Epistylis in the fact
that the ciliary disc is attached to one side of the oral entrance, and is usually elevated
to a considerable distance above the margin of the peristome, like a lid. They are
often seen as commensals on aquatic larvae and Entomostraca.

The loricated Vaginicolinse is not less rich in surprisingly beautiful forms. Vagini-
cola has the sheath erect, sessile, and open at the top. The animalcule is fastened to
its case, protruding its body and spreading its peristome ; at the least disturbance in its
surroundings it instantly retracts, soon to very cautiously again protrude its body. Those
species with a lid to close the case when the animal is withdrawn, have been placed in
the genus Thuricola. T. crystalina is a common species. If the case
is pedicellate and open, the form is a Cothurnia (Fig. 21) ; if, in addi-
tion, there is a corneous lid, it is a Pyxicola; if a fleshy lid, Pachy-
trocha. All these forms may be looked for on Entomostraca and aquatic
plants, like Lemna, Anac/iaris, and Jlyriojyhyllum.

In Platycola and JLagenophrys the cases rest on one side. Fig. 45
represents the charming Platycola dilatata, the brown, laterally at-
tached case occurs on fresh-water plants. The animalcule is quite
similar to those of a majority of the loricate forms. There are two
genera, whose social individuals inhabit common gelatinous matrices,
viz., Opluonella and Ophrydium. One species of the latter genus, 0. diintata, magni-
versatile, may often be seen in shallow fresh and salt water as more or
less spherical green masses, sometimes floating or resting on the bottom, and may easily
be mistaken for algte, such as Tetraspora or JVostoc. These masses are inhabited by

46

LOWER INVERTEBRATES.

myriads of green Infusoria whose structure does not materially differ from tliat of
I^pisti/lis, except the greater elongation of the canal-like extension of the contracticle
vesicle, which ascends to and surrounds the peristome. A notable structure is found
in the thread-like pedicles which unite the individuals of the whole colony. These
appear to be homologous with the branched stalk of £jnsti/lis. In OjiIiryJium sessile
the jiedicle is wanting, the bodies radiating from one point in the mucilaginous en-
velope. 0. versatile and 0. eichornii are known to inhabit American waters.

Sub-Oeder IV. — Hypoteicha.

This sub-order includes numerous families and genera, nearly all of which are free-
swimming ; their bodies are smooth above, with variously disposed cilia below ; they

are usually flattened and elon-
gate. Chilodon cucullulus af-
fords another stock form ; it is as
cosmopolitan as Paramecium
aurelia, inhabiting both salt and
r~f^ ■'^ W^ / \^ >/ '^ / I IF/I^t|f>f fresh water. It has received
0\ \ i\'/-^-\f'^ylJ I § fl I / many names ; its flat, sub-ovate

body has the anterior apex turned
one side. The cilia on the ven-
tral surface are arranged in par-
allel lines. Its pharynx is sur-
rounded by a series of rod-like
teeth. Its food appears to be
diatoms, for these plants are
often found in its endoplasm.
Di/steria armata, described by
Huxley, is remarkable for the
indurated, complex phaiynx.
The oral pit is strengthened by
a curved rod which terminates
in a bifid tootli. This is fol-
lowed by the ])haryngeal apjjara-
tus proper, which may be said to
consist of two parts — an anterior
rounded mass in opposition with
a much elongated, styliform, pos-
terior portion. This part is quite
complicated, and cannot be clear-
ly defined in a few words. On
account of this complicated struc-
ture, and the single ventral stylet, '
it has been considered a rotifer,
but recent research has brought to light facts suflicient to warrant the formation of a
family with this species as the type. A curious genus is Stlchotricha, in which the ani-
malcules secrete a domicile ; several of the species live singly, but in one the stock is
branched, and a social group or colony is the result. This Kent has put in his new genus

Fig. 46. — Scliizosiphon sociaiis, euiatged.

INFUSORIA. 47

Schizosiphon. Stylonichia mytilus, which is abundant in vegetable infusions, illustrates
a type of structure somewhat common in this sub-order : the presence of stylets and
hooked hairs. It is elongate, elliptical, with a slight left-handed curvature, tapeiing
backwards from the centre ; two of the fine anal stylets project beyond the body, the
three long caudal setai are radiating ; there are five claw-like ventral stylets and several
frontal ones. Euplotes also includes well-known forms. They differ from those of the
lastrmentioned, first in being encuirassed, second in the styles, although frontal, ventral
and anal are represented.

Order III. — TENTACULIFERA.

It remains to introduce some typical forms of the order Tentaculifera. Compared
with the orders already described, the specific forms are comparatively few, but their
remarkable structure renders them as interesting. Until recently the Tentaculifera
were not recognized as a distinct order of Infusoria. By Ehrcnberg they were arranged
with the diatoms and desmids. Stein in his earlier publications regarded them as
developmental stages of the Vorticellidae. To Claparede and Lachmann is due the
honor of pointing out their true nature. The term Tentaculifera was proposed by Prof.
Huxley, while Suctoria, — the name applied by Claparede and Lachmann, — has, by
Kent, been retained for the division in which the tentacles are wholly or partly suctorial.
He has also called those whose tentacles are non-suctorial, but merely adhesive, Actin-
aria. The animalcules in their adult life bear neither tiagella nor cilia, their embryos,
however, are ciliate. Maupas claims that adults of some Podophryoe and all the SpJm-
rophrycB are able to resume their cilia and become free. Their food is taken by means
of tentacles developed from their cuticle, the tubular sort terminating in a sucking disc ;
and the protoplasm of the body extending into the tentacles. When an infusorian is
caught by an Acineta and held at the extremity of one of the tentacles, a rupture is
produced in the cuticle of the victim at the point of contact. The axillary substance
of the tentacle penetrates this perforation. The tentacle now increases in size, due,
doubtless, to a flow of sarcode from the body of the Acineta. On penetrating the body
of the prey this sarcode, according to Maupas, mingles with the substance of the vic-
tim's body, and then returns to its place of departure. A nucleus and one or more con-
tractile vesicles are usually present. The Tentaculifera increase by division and by
budding.

Sub-Order I. — Suctoria.

The species of Acineta and its allies are numerous ; the animalcules have many ten-
tacles, while in the genera JRhyncheta and Urnula, there are only one or two ; all are
stalked, some are loricate, others naked. The Sphcerophryce are free forms, frequently
parasitic within other Infusoria. Sphmrophrya sol is found in Paramecium aurelia,
S. stentorea in Stentor rceselii, etc. They are spherical, with suctorial tentacles scat-
tered over their surface. The earlier stages of the next genus are free, and may be
taken for iSphcerophryce, and the latter in turn have been mistaken for the acinetiform
embryos of their hosts. The genus Podojjhrya also includes many species. They dif-
fer materially fi-om the preceding in that they are isedicillate, while some species differ
from others in having the suctorial tentacles in fascicles. To the latter belongs P.
quadripiartita, which has been often seen by the writer on the stalks of jEjnstylis plica-

48

LOWER INVERTEBRATES.

tilts, whose acmetiform embryo it was once regarded. Its stalk is long, the body ovate,
with the upper border divided into four tentacle-bearing lobes in the adult; in the
young there is but one lobe ; this gives place to two, and finally to the full number.
According to Claparede and Lachmann, two sorts of embryos, lai'ge and small, are de-
veloped ; the former enclose a portion only of the nucleus of the parent. According to
Btitschli they are liberated through a specially developed orifice ; the other forms are

produced by the sub-division of the nucleus.
In both cases, at the time of liberation, the
embryos are ciliated like the peritrichous In-
fusoria, with an equatorial girdle and anterior
tuft. In Hemiophrya gemmipara (Fig. 47),
we have a remarkable Acinetan. There are
two sorts of tentacles, viz., a few, centrally
placed, of the usual suctorial type, and a
larger number of prehensile ones around the
border. When the latter are seen under a
high magnification the surface is seen to be
not smooth, but nodular, the component par-
ticles of externally developed granular pro-
toplasm being usually disposed in a spiral
manner around the central axis. The production of embryos by gemmation has been
referred to on a pi-evious page. The genus Acineta has many representatives inhabiting
both salt and fresh water. An interesting species is found in large numbers on the sur-
face of a Mysis taken in the Great Lakes.

Fig. 47. — Hemiophrya gemmipara, magnified
150 times.

Sub-Order II. — Actinaria.

This sub-order includes a few forms in which the tentacles are filiform and prehen-
sile. They are inhabitants of salt-water, and, like their nearest relatives, are mostly
commensal upon aquatic animals.

D. S. Kellicott.

SPONGES. 49

Branch II. — PORIFER ATA.

The sjionges are even now i)0j)ularly regarded as plants, altbough f(ir many years
naturalists have recognized them as members of the animal kingdom, while the investi-
gations of the jiast fifteen years have shown them to be animals of by no means the
lowest type. In the preceding jiages we have seen that the unicellular Protozoa do
not rej)roduce by means of eggs, but by a process of division or segmentation, resulting
in a varying number of embryos, germs, or spores. All of the higher animals, includ-
ing the sponges, are composed of multitudes of cells, each performing its own part in
tlie economy of the individual, and while reproduction by division is frequent in cer-
tain groups, all have recourse to sjiecialized cells or eggs for the perpetuation of the
sjiecies. On account of these differences all multicellular animals have been collec-
tively termed Metazoa, in contradistinction to the single-celled Protozoa. There is
here a similar relationship to that which exists between the spore-bearing and the seed-
bearing ])lants. In an egg-bearing animal there is a specialization of some of the cells
of the tissues and jiarts to form the male and female reproductive elements, just as in
the flowering plant there is a similar specialization of ^ the tissues and leaves to form
the male and female products and the organs of reproduction, and as the latter by the
union of the sexual elements form fertile seeds, so in the Metazoa the union of the egg,
or female element, with the spermatozoan, or male reproductive j)roduct, produces a
fertile egg.

In the Poriferata the development of the sexual elements appears in a simple
form ; parts or cells of the tissues within the body of the same sponge grow larger
than the rest, and become eggs while other cells change into spermatozoa. The
.s]ionges are, therefore, hermaphrodites, and besides they have no external genital or
reproductive appar.atus and no special apertures for the extrusion of the young. It
has been found, however, that some sponges are female, or at least produce few if any
sjierm-beariiig cells, and these sponges in some cases die soon after giving birth to
their broods of young. In most sponges self-fertilization seems to take place ; indeed,
such would appear to be the inevitable necessity since the male and female elements
are enclosed in the same membranes.

Sjionges are all aquatic, are found in the waters of every ]iart of the globe, and in
suitable locations may be exceedingly abundant. 80 far as known they are all seden-
tary animals, constrained with few excejjtions to pass all but the earliest st.ages of
their existence fastened to the same submerged object to which they became attached
in their early youth. The young possess powers of locomotion and can seek out new
places of abode, but the adults must remain in one place and take whatever of food or
fortune the passing currents may bring them. Thus they can only live ami flourish in
places where there are floating clouds of microscopical plants and animals, and their
sjjores. These form their staples of subsistence and must come to them as the rain
comes to the plant. They can use for tlie reception of iood\ only the upper and
lateral surfaces of the body, the lower, attached surface, being of course unavailable
for such purjioses. To this rule there are some exceptions. For instance, Siihcrites
<:ompacta, a sand sponge, has no base of attachment and is apparently capable of li\ing
with either side uppermost; there arc also some wanderers, sponges which ha\-e
vol.. I. — 4

50 LOWER INVERTEBRATES.

broken away from the base and, still living, are rolled about on the bottom. Some of
the commercial sponges are said to be tough enough to stand this.

The sponge is typically, or in its most perfect aspect, a vase contracted at the top.
In nature it has none of the usual signs of symmetry observed in other animals, and is
in most fonns even very irregular. There is absolutely no forward or hinder end,
except in the embryo ; there is no right or left, except again in the embryo. Being a
purely sedentary animal, and having no appendages, it has become and usually is des-
ignated as amorphous or formless. The conditions which influence growth have
caused not only this degradation in symmetry, but they occasion, also, great differ-
ences in form in the same species. Thus, while they may bo called formless in respect
to symmetry, from another point of view they are really animals with more formii
than usual. '

Among those which live near the shores and in the varied conditions of the shal-
low water habitats, there is the strangest diversity. Every change of bottom, every
change in the surrounding conditions of the current or the j^lace to which the larva
may become attached, has some effect upon their aspect. Thus in the same sjiecies
we find flattened sheets, irregular lumps and clumjis, and branching, bush-like modifica-
tions of each of these in every variety, and finally vase-like shapes, either imperfect
and open on one side, or perfect and not wholly without grace of outline. If we pass
from the varied bottom of the Shore-line to one of uniform character, whether the mud
bottoms of the deejier waters of the ocean or those nearer shore, or the sandy shallows,
where the surroundings and conditions of life are more uniform, we find that the
sponges inhabiting these localities ai'e remarkable for greater iiniformity of shape
within the species.

Sponges exhibit most plainly in their forms tlie direct action of gra\ity and the
peculiarities of the base of attachment. In a sedentary animal the fluids of nutrition
would naturally tend to expend their forces primarily, in the early stages of growth at
the lowest points of the periphery, and after buildi/ig the base, cause the sponge to
grow upwards in the direction of least resistance. This is practically what happens,
and if the rock is smooth and free from other animals, some species, liaviiig no heredi-
tary form, will grow in a broad sheet without branches ; but if the base of attachment
be small or crowded, the same sponge will take a bushy, plant-like outline. The force
of growth which otherwise would have expended itself in increasing the sponge hori-
zontally, is diverted by the strain on the sui)iiorts or skeleton to the secreting mem-
branes of the threads, and we find they become thicker or denser where the strain
is greatest, until in some very old sponges the trunks or bases are almost solid. Above,
the branches are arranged so that the form is balanced, and there is the same equal
distribution of the weight around a central axis as in plants and in sedentary animals-
of all kinds. This tendency or response of the animal to the attraction of gra\'itation
by equal growth in horizontal planes, so as to balance one side with another, one
lateral organ with another, I have previously termed geomalism. Geomalism a]ii)ears
in its primitive aspect among the sponges since they are comparatively soft and sup-
ported by a pliable and primitively fragmentary internal skeleton.

It will be seen from these remarks that the form of the sjionge is more largely the
result of the character of the base of attachment than any other cause. When this is
uniform, as in a mud or sandy bottom, the form is either vase-shaped or branching and
comparatively constant ; when upon rocks or irregular surfaces, all forms may occur.
Another correlation has been frequently noticed by the writer. In rapid tide-ways a

SPONGES.

51

species, which is flat or chubby in quiet water, will tend to devolop into branching
forms.

This plasticity of form in response to environment also correlates with the pecu-
liarities of the digestive system. The sponges have thousands of minute cavities
within the body, devoted to i)erforming the functions of digestion. These cavities re-
ceive their food from streams of water, circulating through a double system of tubes,
and flowing in through the narrow meshes of a network, formed in the outer covering
or skin of the body. With this sieve-like structure there is no use for any jjarticular
set of external appendages, and no necessity for any lixed symmetry of foi-m. All that
the sponge needs is a capability to adapt itself to its surroundings and the sole
requisite of success in obtaining food is the presentation of as much surface as possible,
thus securing a large supply of water and accompanying food.

Such an organism requires a peculiar skeleton. Since the internal tubes and mi-
nute stomachs would be liable to compression by the weight of the soft tissues, after
the attainment of a certain size, unless some firmer framework was interposed, we find

Fig. 48 — Portion of a section of a batli-sponge {Sponijia), sliomiig the fibrous slieleton, portions of the
supply and drainage systems, and the ampulke.

in most sponges such a supporting skeleton. In some cases this framework is formed
by a woven mass of elastic threads, of a horny nature ; in others the framework is
composed partly of such threads and partly of stiff and unelastic spicules which may
bo calcareous or silicious, or in still other cases of a network of spicules united by only
a small amount of horny or silicious material. The same isrinciple of construction runs
throughout the whole of the Poriferata ; the skeletons are really networks or scaffolds
of spicules, or of threads permeating all parts of the body, in order to support the
whole mass and keep open not only the digestive ampullre, but also the numerous
tubes for sujiply and drainage.

A skeleton is not, however, an absolute essential in all the members of any Ijranc'h
of the animal kingdom ; thus there are sponges entirely destitute of spicules or threads,
but these are mostly flattened or small vase-like forms, in which the weight is small in
proportion to the strength of the tissues.

In the commercial sponges the skeleton is an intricate mass of interwoven elastic
horny threads, as may be seen by slicing one through the middle (Fig. 48). This network

52 LOWER INVERTEBRATES.

is permeated by numberless tubes, but these can be reduced into two systems, one lead-
ing from the interior outward, and the other leading from the external surface toward
the interior. The first or internal system is composed of several large trunk tubes,
largest interiorly, but branching and becoming smaller as we approach the exterior.
The outer surface of the sponge is ornamented with projecting bunches or ridges of
threads. Between these jjrojections there are numerous dejjressions, the bottoms of
which are perforated by openings of medium size, which we can follow as tubes lead-
ing into the interior by examination of the cut surface of the section. These are the
tubes of the external system. They often terminate abruptly, but here and there are
divided into branches, and we can see that they really diminisli in size towards the in-
terior. Not infrequently these tubes may be traced directly into the trunks of the
internal system, but in this case, their walls are thickly set with the openings of small
tubules which lead into systems of tubes diminishing in size internally, and tlierefore
belonging to the external system. The dried skeleton looks as if there was no room
for fleshy material between the meshes, but tlie increase in size upon wetting a sponge
shows that when in the natural element and fully expanded there is 2'Ienty of room
between the threads for all tlie organs we have to describe.

The surface of the living commercial sponge is of a dark color, and some species,
were they smoothei-,- w'ould remind one of a piece of beef liver. On the upper surface
we can see large crater-like openings as in the skeleton, but the surface is otlierwise
quite different. The tufts of fibres and the depressions between them, which ai-e so
marked in the skeleton, are more or less covered with a skin which conceals all the
cavities and channels. The tufts, however, do show themselves as slight jiromineuces,
while the skin over the intervening depressions is smooth and perforated by groups of
holes. These small holes may be opened or closed at tlie will of the animal, and when
open they serve to admit water freely to the external or supiply system of tubes.
These openings may in many sponges entirely disappear, and new apertures be formed
when needed. This faculty has, however, been greatly exaggerated.

The superficial cavities are lined witli a smooth skin, lighter in color than tliat of
tlie exterior, wliile the sides and bottom are jierforated by small holes, the openings of
the tubules which line the skeletal tubes of the external system and form the flesliy
canals of the sujiply system. These tubes are lined witli a light colored skin and
branch as they descend into tlie interior. Tlie tips of tlie minute branches expand into
glolmlar sacs. These little enlargements, the am])ulhi', ojieu in turn, into small fleshy
tubules whicli line the internal system of tubes of the skeleton. They constitute what
may l)e called a drainage system, and instead of growing less, they increase in size as
they go inward, and by uniting with other similar tubes, they form larger and larger
branches until they finally ojien into one of the central trunks.

These sieve-like openings, the superficial hollows, and the supply system act as
feeders, bringing water loaded with nutriment to the ampullae or digestive sacs. After
digestion the refuse is passed out of the ampulla3 into the internal system and thence
into the large central trunks which finally open on the outside of the si^onge in large
crater-like orifices. lu some sponges these two systems of canals are not distinguish-
able and there is but one outlet to tlie ampulla?.

The outermost covering of the body is an extremely delicate membrane composed
of a single layer of flat cells, giving a peculiar shade of purple bloom to the living-
sponge, but being easily abraded by rough handling. This layer is the ectoderm, ami
is continuous at the edges of the craters with a somewhat similar layer, lining all of

SPONGES.

53

the passages of the drainage system, which should be considered as the endoderra. To
this latter system the amjiullae belong, but the endoderm which lines them is of a differ-
ent character. The tubes of the supply system are doubtless of ectodcrmic origin. The
endodermal cells are usually flat
and have polygonal outlines, v

except in the ampullae, where
they give place to oval or even
columnar cells, the free ends
being crowned by transparent
collars, from the centre of
which ]irotrudes a long flagel-
lum (Fig. 52). These collared
cellshave unusually large nuclei.
The ectodermal cells vary some-
what in outline, according to
position, but are usually hex-
agonal or quadrangular and
rather constant in form. The
cells of the endoderm, on the
contrary, are subject to extra-
ordinary changes, bulging out
into balls on their free side
when gorged with food, or ex-
tending to hair-like cells of en-
ormous length when stretched
across an opening.

Between these two layers
lies the middle or fleshy layer
of the body, the mesoderm.
This is composed of cells, but
the intercelhilar spaces are so
abundantly filled with proto-
plasm that Haeckel and others
consider it as a characteristic of
the sponges. We are, however,
of the opinion that the abun-
dance of intrarcellular substance
has liecn greatly exaggerated,
and that the mesodermal cells
are numerous and closely ag-
gregated. Such we have found
to be the ease with the Calci-
spongiaj and Chalina, and Lie-
berkuhn and Huxley claim the
same for SponyUla. The cells
of the mesoderm vary consideralily in character and appearance. They may be
transparent, granular or deeply colored, globular or elongated, entire or amceboid
m outline, and capaljle of extensive changes by expansion or contraction. In many

i IG. 49. — Section of Halisarca, showing supply (af) and drainage (ef)
systems, tlie ampuILne (amp), and eggs in various stages of devel-
opment (a, />, c, (/, e,/).

54

LOWER INVERTEBRATES.

sponges there occurs between tlie undoubted mesoderm and the ectoderm distinct
layers, the origin of which is uncertain.

One of the most interesting jjoints to the
naturalist lies in the history of the skeleton and
its elements. This consists of two parts, the
thread of binding substance of horn or keratode
and the hard mineralized sj^icule. All authors
ajiparently agree in considering the spicules as
mesodermic, but the origin of the threads has
not been so thoroughly worked out. Bari'ois,
howe\'er, considers them of ectodermal origin
in the silicious sponges, and the author has ex-
pressed the same opinion regarding the fibres of
the horny sponges. In the Chalininre the same
would also a])pear to be true. The skeletal
threads of Chalinula are surrounded bj^ a
special membiane, which I have seen in sev-
eral instances, and which may be called the
jierifibral membrane. This.is composed of flat
epithelial cells, either transparent ordcejily col-
ored by granules. They somewhat resemble the
cells of the ectoderm in outline, but are longer,
fusiform in outline, very closely set, and usually
spirally arranged around the fibre. These are
evidently the cells which secrete the threads,
and in one section I followed this sheath and
found it continuous with the ectoderm. We
can thus readily account for the skeleton of
Clialimda by the presence of invaginated pro-
longations of the ejiiderm which would natural-
ly follow and surround first the vertical threads
and then others arising in all directions. The
differences in the structure of the inner and the
outer portions of the fibres of the Aplysina, and
their often hollow condition, can only be ac-
counted for by this explanation as well as the
fact that in Sponym and its allies the centre of
the threads is frcinieiitly occupied by foreign
matter, carried in from the exterior by the in-
vaijination of the ectoderm to form the sheaths
and subsequently enveloped by the horny mat-
ter secreted.

The form of the s]iicules varies greatly, and
affords good systematic characters. A few of
the forms are shown in the adjacent figure.
Some are pointed at one end, some have both
extremities acute, while others may terminate at one or both ends like anchors. They
may be smooth or variously knobbed and ornamented.

Fig. 50. — DilTereiit forms of sponge spicules.

SPONGES.

55

We cannot hope to disentangle the intricate relations of the parts in such confused
structures as the sponges without studying the history of their development. The
young can always be relied ujaon to jsresent the observer with sinii)ler or more element-
ary conditions, and generally help us materially in understanding and translating the
adult structures.

As we have said, the male and female elements are found within the sponge. After
fertilization, the egg undergoes a regular segmentation, and then the two ends of the
body become distinguishable, one being composed of smaller cells than the other.
Tlie embryo is hollow at this the so-called morula stage, but soon the central hollow,
the segmentation cavity of embrj-ologists, becomes filled in the following manner.
The cells of one end of the embryo become pushed in, much as one inverts the finger
of a glove, and these constitute the inner layer or endoderm of the young sponge.
In this, which is called the gastrula stage, there are then two layers. In the cal-
careous sponges they form a cup with a mouth at one end, but in the c'arneosponges
the gastrula is usually but not invariably solid, the invaginated endoderm completely
filling the interior. The mesoderm is developed between these two layers, but from
which one is not yet known. The spicules begin to be
formed in the mesoderm soon after its apjjearance, and
seem to be due to direct transformation of single cells.

These young larvaj swim rapidly through the water
by means of tlie cilia, or small hairs, wliich clothe the
exterior, and which can be moved like so many oars
with force and rapidity at the will of the tiny animal.
The smaller eiul in the larva of the calcareous sponge
is foremost as the little creature moves aimlessly about.
AVhen it encounters any obstacle it usually exhibits no
ability to back off, but manages by keeping its cilia in
constant motion to get away by rolling around the
olKtruction. At last the embryo settles down, with its
mouth or blastopore below, upon the space to which it
is to become attached. The membranes at this end
form a sort of sucker, which spreads itself out and enables the animal to exclude the

water between it and the surface to which it is being
apj^licd. The pressure of the water holds the sponge
in its place, and on some smooth spots this may con-
tinue to be its only anchorage, but in rougher situa-
tions it naturally acquires additional hold by growing
into any cavities or around any projections.

On soft, nauddy ground fresh-water s]>onges usually
begin to grow upon some small substance, which often
is very small, and then the weight of the growing sponge
may sink a portion of the stalk into the mud below.
This portion then dies, but even when dead it plays its
part and forms an anchor for the whole structure. We
cannot imagine an ordinar}- sponge growing u])on a muddy surface unless tlic water was
absolutely still or the mud hard ; otherwise the tiny creature would be suffocated by
the sediment. The deep-water mud s]ionges of the sea (II>/alonema, etc.) have, ii<iw-
«ver, grown so long on soft bottoms that they have developed a system of threads

Fig. 51.-

■Free swimming young of
Stjcandra.

Fig. 53. — Section of attached embryo
of Si/cnndra ; a, primitive stomach;
6, blastopore: e, ectoderm; ft, endo-
derm; s, segmentation cavity.

56 LOWER ly VERTEBRATES.

which, protruding below, penetrate deeply into the mud, nnd may either serve as
anchors or bases of sujjj^ort. The most curious case of this kind occurs in Tethya
gravata, a globular form, in which the threads form a network below, enclosing small
stones and gravel. Thus the animal carries ballast, and if turned bottom up in the
water it rights itself immediately. When rolled over by the waves upon the muddy
bottoms of Buzzard's Bay, wliere it occurs, it is always sure to end its gyrations
right side u]) like a bit of leaded pith.

The observations of Schultze on the young of Sycandra., one of the calcisponges,
show that the ciliated cells, when invaginated, form an am]>ullaceous sac, confirming
the view that we have always held tliat the typical sponge was a single, isolated
ampulla, surrounded by the two layers of the body. A single ]iore is opened into this
sac, and this completes the likeness to one of the Ascones group. The observations
of Barrois, Carter, Schultze, and Marshall all seem to show that the ampullffi in the
silicious sijofiges have a different develoi^ment. After the larva has settled, a hollow
space appears in the body of the sponge, lined by a non-ciliated endoderm. The
amjHillaceous sacs arise as buds from this endoderm, communication with the exterior
is formed by tubes, which arise as invaginations of the ectoderm, and grow inward,
uniting with the ampulhie.

The evidence at present seems to be in favor of Barrois' opinion, that the water
flows in through these lateral pores and accumulates in the interior, assisting to raise
the soft tissue into a dome or spire, until, at last, unable to withstand the jjressure,
tlie top gives way, and the crater is formed. This accounts for the rise of tlic spire
before the formation of the crater, and gives a reason for its disappearance after the
pressure has been relieved by the formation of an adequate outlet. Certain it is that
the crater is not in any sense the mouth or blastopore of the sponge, as is usually sujv
posed. Thus the cloaeal apertures have no special morphological location, and arise
as i^urely mechanical necessities, as do the excurrent openings of all colonial forms.

The simplest sponges have only a single body cavity, surrounded by ectoderm and
mesoderm, and lined by the inner layers. This typical form or vase shape occurs in
the young of the calcareous sponges and in the adults of the Ascones. Individuation in
these forms is comi)lete and simple ; they are each equivalent to a single ampiillaceous
sac, separated from any other sponge and surrounded by mesoderm and ectoderm. It
is evident, therefore, that when a number of these sacs still remain connected with the
body cavity, each additional sac must be regarded as a l)ud or offshoot from the
coelomatic cavity, and the whole can be regarded as a brandling gastro-vascular sj-stem,
through which water and food are circulated and excrement dischai'ged.

The active collared cells of the ampulke are both structurally and functionally, as
was pointefl out by H. James Clark, similar to the zoons of the flagellated Protozoa ;
they have the same organization, catch their food by means of the same slender lash,
swallow it at the same place within the collar, and throw out the refuse matter
in precisely the same manner. The Flagellata are individuals, each having the
typical structure of the Protozoa, and though in every resjiect simple cells, with
collars and flagella, as in the separate cells of the sponge, they are not shut u]> in sacs
inside of a mass of flesh, but are free or attached animals, getting their food in the
open water. Tliis correlation and the aspect and functions of the cells which form
the tissues of all structures in tlie bodies of sponges and higher animals show us that
all cellular tissues must be regarded as aggregates or colonies, while tlie single cells of
which the tissues are composed are the exact mor]ihological re]iresentatives of tlie

I

-'^4 * 1* ^ # ® « ^ «

'•I, „ .„-- ,, ^^ ^ ^' ^ ^ ^ ft « ® sj f- .-i

to

SPONGES. 57

Protozoa. The sponges are simply less altered than other animals, the cells of the
inner layer still retain some traces of tlieir original structure, and we have to rate the
Poriferata as intermediate in these characteristics between the Protozoa and the
Metazoa.

The word ' individual ' leads to many serious misconceptions owing to its popular
meaning, aiul we use the word zoou for any whole animal or part of a colony of ani-
mals whose structure can he said to embrace the essential characteristics of the grand
division or branch to which it belongs. In this sense the single cell is a zoon, with
regard to the whole animal kingdom, or when we wish to contrast the Protozoa with
the Metazoa. The young sponge, at the period when it has but a simple coelomatic
cavity and one opening, is also a zoon, but it is only a zoon when we wish to consider
the Poriferata by themselves.

We can test this position by comparison with the simplest known forms of sponges,
such as the Ascones. The forms of this group have a vase shapie, with only one open-
ing above, while the pores for admission of water are formed as wanted. The struc-
ture and form of this adult sponge is similar to that of the simplest ampullaceous sac,
and is also similar to that of the young when the coelomatic canity is lirst formed, and
it shows us that all these three forms contain the essential elements of sponge struc-
ture, and can thus be apjirojiriati'ly called spongo-zoijns.

After the three layers are fully formed, the coelomatic cavity extends itself in every
direction liy the formation of ampulke as outgrowths from its sides, but these out-
gi-owths do not carry with them the mesoderm and ectoderm. On the contrary, the
outward growth and the formation of a new ampullaceous sac, which is the nearest
approach the sponge makes towards the formation of a new zoon, takes place wholly
inside of the mesoderm, and the outer layer remains unmodified. This is the case in
all the sjjonges with a thick mesoderm, and even among the higher forms of ealci-
sponges. Among the primitive Ascones, however, a bud from the side carries witli it
all the membranes of the body, and is a repetition of the original zoon, a complete bud
or ' person.'

New craters are formed anywhere as the sponge increases in size, by the conjunc-
tion of canals of the drainage system and without the slightest signs of budding, and
yet Haeckel and others regard each of these craters as a person or individufil. The
mass may grow out solidly into a branch with a dozen craters, then, according to these
authors, it is one dozen small 'persons,' or as it grows out, the dozen small canals may
unite and form one canal and one crater, then it is one ' person.' There are plenty of
examjiles in which such variations occur on the same stock, and we think they j^rove
that the accepted ideas of what constitutes an individual or person among the sponges
with a thick mesoderm and branching gastrovascular canals are entirely erroneous and
founded on the deceiitive resemlilanees of the branches of a sponge to those of other
compounil forms, which really arise from true buds and are true zoons.

Haeckel and others have regarded all the vase-shaped sponges as single individuals
or zoons, but this seems untenable, except in the group of Ascones. It is not uncom-
mon to trace the form of the same species among living sponges from a flattened disc
with several craters to a vase shape, the vase being built up by the more rapid growth
of the periphery. The inner portion of the ectoderm on top of the animal thus be-
comes internal, and the opening above, the crater of one large ' person.' Here the
so-called zoon is formed liy a transformation which can be clearly proved to be the
result of the growth of the external parts. It is evident that the mere fact of the

58 LOWER lyVERTEBRATES.

existence of a cloacal outlet does not necessarily indicate the i^resence of an individual.
We must regard the wliole mass which springs from one base as being an individual,
while the buds or branches wliich may arise from it are not branches, but may be
regarded as the i)rototyi)es of true buds and branches of colonial animals in other
divisions of the animal kingdom. They resemble the branches of other colonies in
aspect, and arise from unequal growth of parts in a more or less symmetrical way, and
may have any outline essential to the ei)uilil)rium of tlie form, but are no more indi-
\iduals than are the arms and legs of a human Ijeing.

Tiie whole mass is the individual, and the fact that it has a branching gastrovas-
cular system is accounted for by the budding of the coelomatic cavity just as the o-as-
tro\ascular system of tlie Hydrozoa and the water sjsteni in eehinoderms is formed by
the prolongation or budding of the walls of the gastric cavity of the larval forms. In
fact the similarity of these parts in the CoBlenterata and Echinodermata indicate to us
that the sponges present a much more primitive condition of the gastrovascular sys-
tem than do any of the higher types. In the eehinoderms, the system becomes sepa-
rated into the gastric cavity and the system of water tubes in the early stages ; in the
Hydrozoa and Ctenophora, the two reniain in connection and a true water system is
not developed. In the sponges there are two systems, the supply or water system and
the cloacal or gastric system, and these two together make a complete gastroA-ascular sys-
tem which, however, is more primitive than either of the other types, combining both
the gastric and the water systems in a double set of inter-communicating canals. It is
difficult to explain the similarities of the water systems among these animals on any
other grounds, and this view enables us to throw some light upon the sinularities of the
cd'lomatic cavity. This cavity is merely the primitive hollow of the body of the
embryo, and in many of the lower forms, as the Hydrozoa, it is the digestive cavity,
the cells being modified for assimilative purposes. This is only the next stage above the
cellular mode of digestion in which each cell performs this function as in the ampulla?
of the sj)onge, and it is an adaptive change both in the structure of the cells and their
function.

If our view of the affinities of the sponges is correct, this cavity in the Ascones is
directly derived from the communal inlet and outlet of some colonial form of Protozoa,
and the water system must have arisen subsequently in response to the budding of the
ccelomatic cavity, and the need of special sources of supply for each bud with its
ampulla?. The correlations in the structure of the feeding cells of sponges and the
aspect and similar functions of the cells which form the tissues of higher animals show
that not only the sponges, but all the Metazoa, however highly individualized, must be
regarded as aggregates or colonies in which each cell represents a zoon of the Protozoa,
and which has derived its structure by inheritance fi'om an ancestral ])rotozoon. That
is to say, there is such a phenomenon as the inheritance by the single cells of a nieta-
zoon of the peculiarities and even the tendencies of the independent individualized
]irotozoon, and from this results the communal characteristics of the raetazoon which
a]i],ears to lie, but in reality is not, a simple individual. The only siinj)le individual in
the animal kingdom is the single unicellulai' protozoon, or a single cell from the tissues
of the Metazoa.

This view, though for a time overwhelmed with ridicult", has of late years obtained
a quite general acceptance. It dates back to an inspiration of Oken in 1805. The
transitions by which it could have taken ]ilace have never been satisfactorily stated nor
can we here do anything more than add another step towards a final solution. It is now

SPONGES. 59

\vell known tliat there is no ascertained limit to the action of heredity, and that not
only observable characteristics, but even habits and tendencies may be directly trans-
mitted from one generation to another. There is a universal and necessary law of
lieredity which can be used in bridging the gap between the Protozoa and the Metazoa
which may be briefly formulated as follows : All animals exhibit a tendency to inherit
the characteristics of their ancestors at, earlier stages than those in which these charac-
teristics first appeared. Thus, if an ancestor or radical form acquired a new character
or took on a new habit when adult, this would tend to reappear in the descendants at
earlier and earlier stages, and in course of time would become carried back to the
adolescent, then to the larval stages, and finally either become useless and disapjoear
altogether, or if useful, and therefore retained, become restricted to embryonic stages.
This law- was first advanced in 1866, by three jjersons, Haeckel, Cojie, and the writer,
almost simultaneously.

The Ascones are certainly, so far as known, the simplest or most generalized of the
Metazoa, and approximate to the Protozoa in such a way that it is possible with the
aid of the law of concentration of development to explain the transformations by which
such an organism could liave risen from the Protozoa. The egg of all Metazoa is in its
first stages a simple cell, and like all other cells is a homologue of an individual or
zoon among the Protozoa. This primitive egg cell has but one mode of growth by
which it forms tissues. It divides or segments and builds up the primitive tissues of
the embryo by a similar process to that by which colonies are formed among tlie Pro-
tozoa. Therefore the egg after segmentation is no longer a single zoon, equivalent to
a single zoon among the Protozoa, but a mass of such zoons, differing from the mass
of a free colony of ama'boid Protozoa in about the same way that the included cells of
an ampulla differ from a colony of Flagellata.

Among colonial Metazoa we frequently find on the same adult stock, individuals
devoted to tlie performance of distinct functions, and having their shape and structure
so modified tliereby as to differ widely from each other, though in their younger stages
they were more nearly alike.

Thus, on the same hydrozoan stock we ma}' find females loaded with eggs, males
carrying only sjierni cells, sexless ])olyps devoted wholly to alimentary purposes, others
with only defensive functions. We have therefore excellent reasons for assuming that
similar transformations took place in the transition from the simple colonies of the
Flagellata to the more complex condition of the sponges, and we can make a picture
of these changes in strict accord with the laws of morphology.

Throughout the Metazoa as well as in sponges, the external layer or ectoderm is
protective and builds the protective armor, scales, etc. ; the mesoderm is essentially
devoted to the formation of flesh and organs of support, while the endoderm is devoted
to the function of digestion, and the elaboration of all the parts concerned in tliis pro-
cess; but everywhere these three layers are derived from one cell (the egg). If now
we imagine a series of changes, beginning with any flagellate protozoon, and follow-
ing out the indications of embryology, we should first have a sheet of attached flag-
ellate feeding forms ; secondly, these surmounting or arched above a base composed
solely of supporting individuals without collars or flagella ; thirdly, the outermost
losing their flagella and collars, would become simply protective pavement cells,
while the central ones retain their digestive functions; the change slowly becoming
more complete, and the central ones acquiring a ca]iability of being withdrawn into
the interior when alarmed. The last step would be tlie inheritance of the invaginated

(30 LOWER INVERTEBRATES.

condition, and this would give the vase-shaped Ascoiies. Tlie inheritance of the in-
vaginated stage or of the primitive differentiation of the colony into protective and
feeding zoons in any encysted egg form would be necessarily attended l>y the forma-
tion of a globular shape in which one end would have cells of a different kind from the
other, one being composed of endodermal cells inheriting tlie digestive functions of the
original colony, while the other would be formed of ectodermal cells arising from the
protective zooiis. This encysted form would be composed of but one layer of cells, and
tlierefore have a hollow interior, and the supporting zoons or meso-
derm would be formed between the other two membranes when it
became necessary by the protozoon method of reproduction by
fission.

We can also reverse this explanation and imagine a sponge,
one of the Ascones, being reduced to a jirotuzoon ; losing first the
form, then the sujiporting layei', then the proteeti\'e cells, and finallv
becoming converted into a layer of zoons, each of which would
closely resemble those to be seen in Fig. 29. The validity of this
comparison may be seen by comparing this figure of Codosiga with
Fig. 53. — FiiigeU:rteii the flagellated am] lullaceous cells of a true sponge shown in Fig.
of .sv/oi°"}to'."''" ^ 52 ; and the comparison will also gain when we recollect that in

the young of the flagellated jn-otozoon the stalk is absent.
The normal action of the law of concentration and acceleration of development
would alone have caused such changes in the modes of growtli of the Metazoa if the
latter were really the descendants of the Protozoa, and this series of transformations
is included when we say that the Metazoa, in accordance with this law, have inherited
the tendency to form colonies or tissues by fissiparity, at an early stage in the exis-
tence of tlie cell or zoon. Thus, the individualized protozoanal stage has become con-
fined to the earliest periods of existence instead of being more or less permanent and
characteristic of the later stages of growth as in the Protozoa. When the colonj- be-
comes embryonic the process of multiplying by division is, as a necessary consequence,
also accelerated and concentrated, and tissues are rapidly formed for different pur-
poses. We can tlierefore, without calling to our aid any but the well-known effects of
habit and the law of concentration of development, account for the segmentation of
the egg, and tlie subsequent tendencj' of the ])riinitive tissue to give rise to the three
layers of the j\[etazoa. The fact that certain cells become differentiated into eggs, and
others from the same or other layers, into spermatozoa, is not more reniarkal)le than
that certain zoons of many colonial IVIetazoa, like the hydroids, are exclusively egg-
bearers, while others are solely sperm-bearers. The fact that tlie male element seeks
out the egg and becomes merged in it, is paralleled by the process of conjugation among
the Protozoa. The sperm cells of the Metazoa, like the germs of the Protozoa, arise by
division of a single cell, and, although frequently of similar shajie to and swimming
freely like many protozoon germs, they do not wait until maturity before conjugating
Avith the females. This is plainly only the inheritance of the tendency to conjugate
at an earlier stage, and is a natural result of the law already laid down.

It is well known that there is a tendency to reproduce after conjugation, and that
conjugation is performed by Protozoa of different sexes, and also that there are
sexual colonies among the higher Protozoa. Tin' result of differentiation or progress
is evidently towards the formation of sexual differences in the Protozoa as in otlier
branches of the animal kingdom, and if our view is correct, we ought to expect that

SPONGES. ^ 61

the Metazoa, springing from the Protozoa, woiihl show siniihir tendencies toward dif-
ferentiation of the colonies. If, as in the sponges, the lower forms had male and
female cells in the same body, then the progress of differentiation should lead to a
more decided separation of these functions so that some would produce only female
and others orjy male cells. In otiier words, the complete separation of the sexes would
take place by a jjerfectly natural transition, and we should have male metazoons and
female m^etazoons.

The sponges are frequently regarded as degraded Metozoa, but to the author this
view seems highly improbable. Iluxley first recognized the systematic imjiurtance of
the sponges, but contrasted them as a division with the rest of the Metazoa, while
MacAIlister, and subsequently the author, gave them their true taxononiic rank as an
indejiendent branch of the animal kingdom.

Class I. — CALCISPOXGI^E.

This division is somewhat inajipro]iriately named for the reason that some of the
genera have no skeletons, but this objection might, with equal justice, be made with
regard to the names applied to the other groups. The animals of this class have fusi-
form or cylindrical bodies which may be single with one cloacal aperture, or branching
\vith an ajierture at the end of each branch, or more or less solid as in the other
sjjonges. When a skeleton is present, the spicules which compose it consist of carbo-
nate of lime, and their longer axes are arranged in lines parallel with the canals, that
is at right angles to the inner and outer walls of the sponge.

Okdeu I. — PHY8EMAEIA.

This order contains tlie remarkable genera, ILilipJiysema and Gasfrophi/sema,
Avliich, according to Ilaeckel, are nearer in form and stnu-ture to his archetypal animal
form, the gastrula, than are any other adult animals. They are small and vase-shaj^ed
in IlaJiphyseriur, wliile Gastrophi/.'<eina may have from two to five chambers. There is
but one aperture above, and the water is drawn into this by ciliary action. According
to Haeckel, the body wall consists of but two layers, the ectoderm and the endoderm,
but it is evident that the ectoderm of the German savant can be nothing else than
mesoderm, for it is composed of loose cells and intercellular pu'otoplasm, wdiile the true
ectoderm of all sponges is a simple pavement ejiithelinm and never a compound tissue.
In Haeckel's figure, tlie whole interior of Hali.tphi/nema is paved with ciliated cells,
among which are interspersed amceboid cells. Both Ilaeckel and Bowerbank deny the
existence of pores, and it is not likely that even transitory openings would have
escajied their observation.

The strangest part of the historj-of the Physemaria is that both Carter and Saville-
Kent claim that ILiUplnisema is a true protozoiin, and Kent's figure, which is as
specific as Haeckel's, depicts a true foraminifer. These observations render it very un-
certain whether the group should be referred to the sponges or to the Protozoa.
Gastrophysemd, may be a true sponge, and we therefore describe the order in this
connection. Mr. J. A. Pyder describes as an American representative of the group, a
curious club-shaped animal with a tough cortex ;in<l a cellular interior, under the name
Camarapthyaema.

62

LOWER INVERTEBRATES.

Order II. — OLYNTHOIDEA.

These forms diftVr from those of the last order, in having a skeleton of calcareous
spicules. These may he either straight and needle-like, or one end may bear three or
four rays. Tiie spicules, which are of mesodermal origin, are arranged at right angles
to the inner and outer walls of the body in tlie tube or vase-shaped forms, and the
rays being interlaced, afford a firm scaffolding for the suj)]Jort of
the walls. Here, as among the Physemaria, Haeekel claims that an
outer epithelial membrane is absent, but Grane, Schultze, Metschni-
koff, and others have repeatedly demonstrated the existence of a
true ectoderm, and the writer has seen this membrane several times
in the living sponges. The species are usually colorless, generally
of small size, and although abundant along our coasts must be
looked for carefully under stones and upon sea-weeds. They are
found exclusively in shallow water, aiul, with few excei)tions, do

Fig. 54. — Ascattis, one 'i i ,

of the Ascones group, iiot occur OH muddy hottoms.

SrB-C)RDEi; I. — AscoxEs.

These forms have a vase-like shape, are thin-walled, and have a distinct skeleton
formed of a single layer of triradiate .spicules, their bases outward, while the pores of
the supply system are formed as they are needed, through
the sides. The inner or coelomatic cavity is lined with
flagellated and collared cells, while these, of course,
are not found in the transient supply-canals, which,
according to Haeekel, are but temporary openings in
the sides of the sponge.

Sub-Order II. — Sycones.

The typical form for the members of this group is
that shown in the figure of Scycandra ciliata. The in-
dividuals are attached by the base or
small end, and are very like those of the

Ascones, but are stouter and more frequently spindle-shaped, while the
walls are thicker and more opaque. They are, however, quite dis-
tinct in their structure. The flagellated and collared cells are con-
fined to the canities of the permanent suppl}- canals, where they occupy
special cavities, the ampullaceous sacs. The cells of the coelomatic
cavity are flattened and similar to those of the ectoderm. The meso-
derm is very thick, and the canals ]-adiate with great regularity from
the cavity of the sjionge to the exterior. The outer part of each canal
represents the supply, and the inner, the drainage system. The spic-
ules are usually in two rows, their radiated bases being turned, respec-
tively, inwards and outwards. "While the living species are some-
what numerous, but one fossil genus is known, and this is of Jurassic age.

Fig.

55. — Diagrammatic section of
Ascaltis.

Fig. 5G. — •ici/can-
dra ciliata.

SPOXGES. 63

Sub-Obdee III. — Leucoses.

The hiii'hor position of this grou]) is sliowii by its greater complexity-. The meso-
derm is tliieker than in the last sub-order. The canals of the supiply system are irregii-
laily branched and frequently anastomose with each other, forming cavities near the
outer surface. The collared cells are distributed along the smaller canals in the lower
forms, while in the higher they are contined to the ampuUaceous sacs. The Leucones
represent tlie nuissive growths of the Keratosa and Silicea, but usually have a common
or united cloacal aperture and are composed of consolidated tubes. Zittel considers this
group a lineal descendant of the next, a view which does not seem to be justified by the
morphology or the mode of development of the nidividuals of the group. No fossil forms
are known.

Sub-Order IV. — Pharetkones.

This division was established to contain a number of forms which occur as fossils
in the rocks between the Devonian and the end of the cretaceous jjeriod. The author
is inclined to consider the genus, Trichonella, which is represented by a species in
Australia, as a living member of this group. Tlie sjncules are so united as to form
irregular threads, and sometimes a very intricate network. The canal system was
branching and irregular, while the mesoderm must have been very thick.

Class II. — CAE:NE0SP0^GI^.

With increasing knowledge the multitude of forms comprised in this class will
doubtless be separated. The common characters are a very thick mesoderm, the ecto-
derm and endodenn similar to that of the Leucones, and the supply and drainage
system as described above in the commercial sponge. The skeleton may be either com-
posed of horny material (keratode) or partly or entirely of silicious spicules. The
skeletal elements are radiately or irregularly arranged according to the plan of canal
system which it su])poi-ts. One order has no skeleton, but the form and structure
show it to belong to this class.

Order I. — HALISARCOIDEA.

This order, which Haeckel calls MyxosjKingia^, embraces but a single genus of
fleshy sponge, known as Halisarca. One species is common on our shores, and also on
those of noi'tliern Europe. The animals grow usually in flat masses or little bunches
of a dull color, coating rocks or surrounding the stems of marine plants. The general
structure can be seen in Fig. 49. With a fleshy nature, of course no fossils of this
order can occur.

Order II. — GUMMININ^.

These are tough and leathery sponges, the external layer forming a cortex which is
partly composed of tibres, which also permeate the central mass sun-tiunding the canals,
and also penetrate the mesoderm. Their composition is still unknown. The genus
Chondrilla has star-shaped silicioxis bodies in the coitex which are not found in Gum-
minia and in the other genera. No fossils are known.

64 LOWER INVERTEBRATES.

Order III. — KERATOIDEA.

Tliese are the true horny sponges, ami from an economic point of view, are the
only ones which have any practical value. The skeleton consists of fibres of S]ionge-
horn or keratode, forming a network in the mesoderm. They are littoral forms not
usually found in water more than seventy-five fathoms in depth. They generally avoid
sandy or muddy localities, preferring rocky ground or coral reefs. Passing by the
genus DarwincHa, for which a sub-order has been formed, we come to the sijonges of
commerce.

Sub-Order I. — Spongin^e.

The Sponging are characterized by having the fil)res of the skeleton solid, but in
places where the water is filled witli fioating matter, they nsunlly have a core of
foreign material, a fact which we have previously mentioned.

The marketable kinds are all of one genus, Sjwngia, that from whit'h all the
sponges derive their common name. There are only six species with, howevei-,
numerous varieties, which are offered for sale, and in fact these mux be reduced to
three species, if one so chooses. Three of the species are fi-om the Mediterranean
and the Red Sea, and three from the Baliamas and Florida. Other species of this
genus have a very general distribution, but they are all confined to the equatorial
and temperate zones within an area on either side of the equator M'hich is limited
by the isotherm or average temperature for January of 50° F. The Spongia gram-
inea and S})ongia cerrehriformis are occasionally used in Florida and Bermuda, but
are not exjiorted.

The marketable sponges owe tlieir excellence to the closeness, fineness, and resili-
ency of the interwoven fibres of the skeleton. The Mediterranean appears to be
particularly favorable to the production of specimens with skeletons possessing these
desirable qualities in the greatest perfection. Those from the Red Sea are next in
rank, while those of our own shores, though corresponding species to species with these
and the Mediterranean forms, are coarser and less durable. Thus iS2)0}igia equina,
the Horse or Bath Sponge of the Mediterranean, is finer than the iS/iongia gossi/jjina,
the Wool Sponge of Florida and Nassau, though it otherwise resem.bles it closely.
Spongia zimocca, the Zimocca Sponge, represents in the Mediterranean waters the
much coarser tSpongia corlosia and Spongia dura, the Yellow Sponge and Hard-head,
on the American side. Spongia adriatica, the Turkey Cup-Sponge an^d Levant
Toilette-Sponge of the Mediterranean, answers to the finest though not the best of our
sjionges, Spongia tubuUftra.

It is probable that the Red Sea and the MediteiTanean were both colonized by
sponges from the Caribbean Sea, and, strictly speaking, the six marketable species
ought to be classed as three species with six jirincipal varieties, differing from each
other according to their habitat. This conclusion is borne out by the facts that tlie
Caribbean Sea contains more species of this genus than any other locality, that no
marketable sponges are found in the Indian or Pacific oceans, and that the differences
in quality cited above are occasioned in these and other sponges with fibrous skeletons
by any change from shallower to deeper water, or from water loaded with sediment to
clearer waters. In each of these cases a finer sponge is the result, and this correlates
directlv with the fact that even in the Mediterranean the marketable kinds are found

c

SPONGES. 65

in waters which are probably very rarely reduced, even during the month of January,
to 55°, and perhaps for the best qualities not below 60° F.

Marketable sponges are found in the Mediterranean on the coast between Ceuta on
the African side, and Trieste on the Adriatic. None are found in the Black Sea,
on the coasts of Italy, France, or Spain, or the Islands of Corsica, Sardinia, the
Balearic Islands, or even Sicily. The sj)ecies do not usually appear in water deeper
than thirty fathoms. They are gathered by means of hooks on long poles, or directly
by the hands of divers, or, as in the case of some of the coarser kinds, dragged up
roughly by dredges. When secured they are exposed to the air for a limited time,
either in the boats or on shore, and then thrown in heaps into the water again in pens
or tanks built for the purpose. Decay takes place with great rapidity, and when fully
decayed they are fished up again, and the anim.il matter beaten, squeezed, or washed
out, leaving the cleaned skeleton ready for the market. In this condition, after being
dried and sorted, they are sold to the dealers who have them trimmed, re-sorted, and
put up in bales or on strings ready for exportation. Tliere are many modifications of
these processes in different places, but in a general way these are the essential steps
through which the sponge passes before it is considered suitable for domestic purposes.
Bleaching-powders or acids are sometimes used to lighten the color, but these, unless
very delicately handled, injure the durability of the fibres.

The first fossils which undoubtedly belong to this group occur in the carboniferous
rocks, Carter having described a Dysidea from this period, but masses supposed to
belong to the Sj^onginiE have been found in much older rocks.

Sub-Order II. — Aplysin^.

These sponges have a skeleton composed of fibres which are hollow or filled with a
soft, friable core, and there are no foreign materials introduced from the exterior.
The fibres are not as elastic as those of the Sponginre and generally are much larger
and coarser. The sponges are dendritic or grow in sheets, often of considerable size.
The skeletons are more open in structure than in the last sub-order, and frequently the
fibres have a fan-like arrangement. No fossils are known.

Order IV. — KERATO-SILICOIDEA.

As the name implies, this division forms a transition between the horny and the
silicious sponges. The skeletons are formed of solid keratose fibres and silicious
spicules.

Sub-Order I. — Rhaphidonemata.

In this group the spicules are of one kind only, usually with pointed ends, and are
loosely arranged in the vertical and horizontal fibres of the skeleton, and covered by
the keratode, though often but slightly bound together. The keratode is light-colored
or transparent. This division is represented on our eastern coast by the well-known
Dead-man's-finger Sponge, Chalinula oculata. This is a bushy form, common on piles
or rocks, especially in tide-ways where there is a considerable current of clear water.
It sometimes grows to a height of two feet. The cloacal openings are small and
irregularly scattered over the surface of the branches, while the pores are imperceptible
to the naked eye. The color is brown, sometimes softened by a warm undertone of

VOL. I. — 5

m

LOWER INVERTEBRATES.

pink. The fibres of the skeleton are light brown, and friable when dry. The fleshy
parts disintegrate so readily after death that these sponges cannot be kept for any

length of time even in the strongest alcohol. Tuba is
another genus of this grou}). No fossils are known.

Sub-Order II. — Echinonemata.

The spicules of the Echinonemata are of two or
more kinds. The simple smooth or double-pointed
ones usually lie in the fibre, the rough single-pointed
ones, with a more or less expanded base, stand out
from the keratode, leaving the point bare. Defen-
sive surface spicules are often present.

This sub-order is represented on our coasts by
Microciona prolifera, which grows abundantly in the
pools and tideways south of Cape Cod. When in still
water and on a smooth surface it forms a thin, smooth
sheet, but under other conditions it tends to gi-ow up-
rio;ht, and form branching masses a few inches in
height. The color is a bright orange red, producing
rich effects in pools where much of it is present.
No fossil Echinonemata are known.

Sub-Order III. — Monactinellin^.

In this group the fibres are composed of straight
silicious spicules, while the amount of keratode is very
slight. The most common form is the Cruml)-of-
bread Sponge, Halichondria panicea, which lias a
world-wide distrilmtion, and occurs ]ilentifully in a dried state upon our beaches. It is
almost as light as dried bread, and when well bleached is very white.

Another form, Suherites compacta, occurs on the coast south of Cape Cod, and is
the only form in that region which is alile to live upon the shifting sands. The pores
are so small, and the structure so dense, that the sand cannot obtain an entrance, while
its lightness keeps it from being buried. Specimens securely anchored have been
found, and evidently the usual free condition is an acquired adaptation to a habitat on
a sandy bottom. They are washed ashore in considerable numbers, and so fine and
homogeneous are their spicules that the skeletons are said to have been formerly used
for polisliing silver. It grows in flattened masses of a yellow color, but the skeleton
when bleaclied is white. Another species of this genus also frequents the sands north
of Cape Cod, but finds more congenial accommodation on the shell of a species of
gasteropod, nearly all of which, in certain localities, bear a sponge.

Some of this group have accustomed tliemselves to lead a life of borers, and though
not successful with hard rocks they are very destructive to the shells of various
molluscs, and even to limestone and marble. Cliona sidphitrea, a very common form,
is the most remarkable of these borers. It penetrates and excavates chambers in the
shell of a mussel for example, and then, after causing the death of the animal, it will
entirely enclose and resorb what is left of the shell. Not content with tliis conquest it

I'uba labijrinthlfonnis.

SPONGES. g7

often proceeds to grow around stones, or to take in sand until its flesh is full of such
indigestible ballast. Such specimens will sometimes be a foot long, and weigh several
pounds. Occasionally this form is found attached in the usual maimer, and when the
locality is free from stones or sand the specimen is clean and free from such encum-
brances. In the Mediterranean this genus plays no small part in the disintegration of
the limestone rocks of the shores. It is evident that this sponge is a borer from inclina-
tion and not from necessity, and also that the inclusion of sand and stones is not needed,
but is probably due to the effort to become attached to any object within reacli. It is
difficult to explain the boring except as a chemical process, but no one as yet has been
able to detect any acidity in the secretions. It may be, however, that it is accom-
plished by the silicious spicules on the surface. That they are not tlie sole means of
boring is shown by the recent observations of Nassonow, who ascertained that the
young began to bore before the formation of any skeletal structures.

The Monactinellidan forms in the palfeozoic rocks are uncertain, though Zittel
records Cliona from the Silurian, and two genera in tlie Carljoniferous. The first
undoubted forms occur in the Jurassic.

Sub-Order IV. — Potamospongi^.

The Fresh-water Sponges, in our opinion, form a group of sub-ordinal rank. The
skeleton is similar to that found in the last group, but a very important difference is
found in the reproduction. In these fresh-water forms there are found what are known
as winter buds or statoblasts. These are protected by an outer coat of sjiieules of a
peculiar form, wholly unlike anything else found in the sponges. They may be as
simple as the spicules of the sponge skeleton, and arranged flatwise in the corneous
wall of the statolilast, or they may be shaped like a collar stud (birotulate), and
arranged vertically. There seems to be a deiinite line between these two types, and,
in fact the sub-order has been divided into two families upon these cliaracters,
and named the Lacustridre and the FluviatilldaB respectively. About ten genera have
been described by autliors from the fresh waters of all parts of the globe. They are
usually green in color when exposed to the light, but when found under stones or in
shaded localities are of a brownish hue.

They have a decided affection for clean water and hard bottoms, being in large
part attached to stones, logs or plants, but will grow sometimes on nniddy bottoms.
In such cases the young anchor themselves to small sticks or stones, and thus secure
themselves from being choked by the mud.

The sponge dies during some cold spell in the autumn, and their quick decay
in large quantities is one of the principal causes by which the Avater supply of even
a large city may be vitiated. They seem to be the cause of the peculiar smell
known as the "cucumber odor," and render the water extremely disagreeable as a
beverage.

The preservation of the species is accomplished by the statoblasts which retain
their vitality through tlie winter, usually enclosed in the skeleton at the base of the
colony. They develop in the spring, producing new colonies. Mr. Potts, of
Philadelphia, accounts for the large size and rapid growth of the sponges in the
spring by the coalescence of numbers of the young which develop within the
meshes of the same old base. Tliis author asserts that he has repeatedly observed
that the young sponges from the statoblasts build ujion the undecayed remnants of

68

L 0 WE 11 IN VEll TEBRA TES.

the Ir.st year's skeleton as if it were a trellis, which, when once constructed, could be

used repeatedly.

This is not linrd to believe, since two branches of the same sponge will unite if

brought in contact, and even two sponges
of the same sjiecies will not infrequently
combine to form a single specimen. A
certain proportion of some of the fresh-
water sponges does outlast the winter,
and these old skeletal frames frequently
contain many statoblasts.

Certain of the fresh-water sponges in
tropical countries have to pass through
a dry season, and it is supposed, with a :
considerable amount of probability, that
their statoblasts can undergo dessication
without loss of vitality, and even that
they may be carried by the winds, thus
affording the starting points for colonies
in new localities when the rainy season
sets in. Some forms are described as
having; no statoblasts.

Order IT. — SILICOIDEA.

This, the highest order of the sponges,
is characterized by having the skeleton
almost entirely composed of silicious
spicules.

Sub-Order I. — Tetractinellin^.

This group can be represented by
Tethya, in which the skeleton is radia-
tory. The ty])ical sjiicules have a long,
straight axis and three cur\'ed arms,
reminding one of an anchor, or more
accurately, a grapnel. There are also
long, straight sjjicules with both ends
alike, and star-shaped silicious bodies.
By the latter these sponges are allied
to the Gummininte. Geodia is another
remarkable type in this group, with ex-
tremely thick and unusually large in-
ternal spicules. When dried, these
sponges are as hard as if carved out of wood. According to Zittel, the greatest
authority on fossil sponges, this sub-order first appeared in the carboniferous, but
was represented only by isolated spicules until the genus Geodia. appeared in the
Jurassic.

Fig. 58. — Eiiplectella aspergiUu7n, Venus flower-basket.

SPONGES.

69

SUB-OrDEK II. — LlTHISTIN^.

This group is composed of fossil forms in whieli the skeleton is made up of rather

very strong and solid

irregular star-shaped radiating bodies, firmly united. Thus,
skeleton was constructed, which has consequently been
well preserved in the rocks. The normal form is a mass
with numerous cloacal apertures of average size on the
upper surface, but forms quite as often grow in vase-shapes,
with the cloacal ajiertures on the inside, or like a pear, witli
the apertures on top. The large opening in the vase-shaped
forms is usually described as a cloaca, though, as we have
seen, it is not so in reality. The type appears in the genus
Atdacopium of the Silurian, though Zittel thinks that some
of the Cambrian forms may belong liere.

Sub-Okder III. — Hexactinellin^.

The glass sponges are remarkable for possessing six-
armed sj)icules. Two of the arms may be almost indefin-
itely lengthened and bound together with others in threads
closely resembling spun glass. In others they may be
shortened .and split into the semblance of flowers with
narrow petals. The glass sponges remind the observer of
the calcareous sponges, but the resemblance is merely
superficial, and not so important as it at first ap)3ears.
Though the Euplectella is hollow and has apertures
through the wall as do the Calcispongise, they do not
lead into radiating canals, but into areolar tissue and com-
municate with the anipulhe by means of numerous aper-
tures in the walls of the sacs. The outlets of the sacs are
large and open internally into the tube. The external and
internal walls are supported by the interlacing arms of the
crosses or hilts of the spicules, and as these are arranged
with great regularity, the surface of the skeleton is divided
into squares. The pores of the outer surface are usually
situated one in each of the quadrangular intervals, and the
cloaca occupy a similar position on the inner wall. The
top of the sponge is closed with a network of threads,
between which occur, as in Hyalonema, the true cloacal
outlets. In fact Euplectella may be regarded as a hollow
Hyalonema.

Hyalonema was at first known only by the stem which
was highly prized as an ornament. The natives were in the habit of cleaning off the
sponge body from the upper part of the stem, and then reversing it in a suitable
standard. It was sold to strangers as the skeleton of the parasitic jwlyj^s {Pahjthoa)
which live habitually on the stem. Scientific men were at first deceived, and the true
character was not discovered until 1860, when Max Schultze found the sponge tissues.

Fio. 59. — Iliialonema, glass-rope
sponge, 'rile stems are covereti
with parasitic polyps, a, polyps
enlarged; b, perfect sponge.

70

LOWER INVERTEBRATES.

and showed that the polyps were but commensal parasites, having nothing to do
with the formation of the long stem of silicious threads which resembles a plume
of spun glass.

Fm. (iO. — Holteiila carpeiUeria.

This genus may be expected in depths varying from forty to one hundred fathoms
in northern seas, and in deeper water as we go towards the tropics, apparently requir-
ing an average temjierature below 40° F. The sponge itself in the natural state, is
not as attractive as Euplectella, being of a light-h>rown color, and friable when dry.
The top is usually occupied with a number of cloacal apertures surrounding a central
jirominence which is in reality the end of the stem. The stem is spun by the tissues

SPONGES.

71

M^B:^^%

as a supporting column of elongated spicules bound together and growing in a spiral
as the animal progresses u]nvards.

The lower end of the stem becomes frayed out, and sinks into the mud as the ani-
mal grows, but constant additions to the upper end compensate for this and form a
column which sometimes reaches a foot in length. In Fig. 59 we see on the rio-ht
a perfect specimen. The stem in the living
sponge is always enveloped in the fleshy tissues.

In Holtenia we have a different type of
sponge, similar in shape to the members of the
Calcarea, but the resemblance goes no further.
The star-like beauty of the external covering of
spicules, and the singular profusion of anchor-
ing threads which are formed below, are sho^vn
in the adjacent figure. Dactylocalyx is another
of the open vase forms which occur in this sub-
order.

The fossils are very numerous, and it is
supposed that several of the Cambrian sjionges
may belong here, though Zittel cites only cer-
tain Silurian genera like Astylospongia and
Protospongia as undoubted Hexactinellids.
One of the best known of the fossil tj-jies is T^entriciilites, our figures of which show,
not only the general shape, but the structure of the skeleton as well.

^rimnwr

Fig. 61. — Section of the outer wall of Ventriculites
simplex, sliowing the structure of the silicious
network.

Alpheus Hyatt.

Fig. 62. — Spicule of Pheronema.

72 LOWER INVERTEBRATES.

Branch III. — CGEI.ENTERATA.

The Coelenterata embrace tlie jelly-fishes and corals, or more accurately speaking,
the Hydrozoa, Actinozoa, and Ctenophora. In the first and last of these divisions
fall most of those animals which are commonly known as the Medusse, while the
Actinozoa include the true corals and their relatives. The endless variety of names
which one encounters in this groujj need not lead to confusion, and if considered in the
light of the liistorical development of the study, indicates those various characteristics
which have from time to time attracted the attention of students of these animals.

Of general terms used to designate the group, that of Zoophytes is one of the
oldest. In the infancy of natural science, when superficial observations took the place
of more accurate anatomical studies, it is not to be wondered at that the likeness of
these animals to plants led to the present name. One of the first comparisons which
the novice makes, on seeing these animals for the first time, is that they resemble
closely members of the plant world, and in maturer studies we are continually meeting
similar resemblances of a deeper-seated nature

The Coelenterata include two of the large divisions of the Radiata of Cuvier, who
first outlined their characteristics in the masterly manner which marks all his works as
models of zoological research. The name Ccslenterata dates back over a quarter of a
century (1847), to the profound investigations of these animals by Frey and
Leuckart, by whom it was first used.

The limits of the subordinate group of Hydrozoa are in many particulars obscure,
and while many naturalists prefer to include in it a large group of gelatinous animals
called the " sea-lungs," comb-bearing medusae known as Ctenophora, others, from the
close likeness of their young to the larvae of the star-fishes, set these apart as a separate
group. The Hydrozoa as here considered include the Hydroidea, the Discophora, and
the Siphonophora, and contain by far the larger part of the true Medusa.

The term Acalejihae, common in many writings on these animals, is almost synony-
mous with that of Hydrozoa as here used. By many it is also made to embrace the
Ctenophora. The term was long ago used by Aristotle, and refers to the stinging
powers which many of the Medusa? have. Given by many authors a greater or by
others a less extension, it has been wholly abandoned by most of the leading students
of these animals.

The Actinozoa or corals are marshalled under two divisions, the Actinoid, or true
reef builders and their allies, and the " sea-fans " and " sea^whijiS," which are called,
from more or less fanciful reasons, the Halcyonoids.

The single anatomical feature which is common to the groups mentioned above, to
which, in point of fact, they owe the name of Cffilenterata, is the identity of a stomach
and the body cavity. In the simplest forms these cannot be distinguished from each
other, and in the higher genera there is but a slight differentiation of one from the
other.

J. Walter Fewkes.

Gorgonia cenxosu, to whicli is attached a skate's egg, natural size.

HYDROIDS.

73

Class L — HYDROZOA.

Okder I. — HYDROIDEA.

In the year 1703, that charming old scientific gentleman, Anthony Van Leeuw-
hoek, of Delft, sent a very interesting paper to the Royal Society of London. In this
article he tells us that " the water of the river Maes is brought by means of a sluice dur-
ing the Summer flood, directly into our town, and it is as clear as if the river itself ran
through the town. With this water comes in also a green stuff of a vegetable nature,
of which, in a half hour's fishing, I got thirty pieces, and put them into an earthen pot
together with a large quantity of their own water. I took out several of these weeds
from the pot, one by one, with a needle very nicely, and put them into a glass tube of
a finger's breadth, filled with water, and also into a lesser tube, and caused the roots of
the weeds to subside leisurely ; then viewing them with my microscope, I observed a
great many and different kinds of animalcula. About the middle of the body of one of
these animalcula, which I conceived to be the lower part of its belly, there was another
of the same kind, but smaller, the tail of which seemed to be fastened to the other."

Our author, in the latter part of his article, assures us that he saw the smaller ani-
malculum separate itself from the larger, and enter upon an independent existence ;
moreover, that he also determined by his microscope, the formation of a minute bud
upon one side of the anunalculum, which grew into an animal, perfect in shape, size, and
all particulars, and then detaching itself from its parents, floated free in the water.
That was the first discovery, so far as all the records give evidence, of the very wonder-
ful animal, which is now called Hydra, and which in many respects, both
in structure and in mode of life, is a very good type of its order, the
Hydroidea, and at the same time of the class of Hydrozoa. The body
of Hydra, which is entirely soft, having no skeleton without or within,
easily changes shape, and when entirely contracted, has the a])j)earance
of a small dot or particle of gelatinous matter resting on the surface of
the aquatic plant, chip, stone, or whatever may be the object in the water
to which this small creature has attached itself. Watching it slowly
expand in a dish of fresh water, it is seen to display a long, slender
cylindrical body, which, in Hydra viridis, is bright green, while in H.
fusca the color is light-brown. The base, or that end by which Hydra
fastens itself, is termed the disk or foot, and the external cells of this
part of the body secrete a gelatinous substance, which, hardening some-
what in the water, enables it to attach itself at will. Toward the
anterior or free end of the body, are a variable number of long, slender
processes, the tentacles, which are arranged in a single circle or wreath.
Within the ring formed by the bases of the tentacles, the body tapers
to a rounded elevation, where the mouth is found, and this tapering
portion of the body which extends beyond the retracted tentacles, is
known as the proboscis or hypostome.

Within the body there is a cavity extending from one end to the othei-, from the
base to the mouth, and, as these processes are hollow in Hydra, to the tips of the
tentacles. Not only the body, but also the tentacles are very expansive and con-
tractile, and seldom retain the same shape and position for more than a few minutes.

Fig. 63. — flyrfro
fusca witli
young bud-
ding from it.

74

L 0 WER IN VER TEBRA TES.

When tliey are fully contracted they appear as so many knobs or bosses on the distal
end of the body, and wlien fully expanded, I have seen them three and even four
times the length of the fully elongated body. The tentacles are very sensitive, and if
touched by some foreign object in the water, they rapidly contract, and the body also
sharing in the contraction, the entire creature is withdrawn as much as possible from
the area of disturbance and danger. ILjdra has been observed in two or three rare
instances to move from place to place by standing on its head, so to speak, using its
tentacles as feet, by which it attaches itself, then it arches the body and attaches the
foot-disk, releases the tentacles, straigiitens the body to arch it again, and so liitches
along like a measuring-worm or geometrid larva. Another very peculiar form of loco-
motion is described by Marshall, of Leipzig, as seen by him in certain ILjdrm found
in brackish water. In this case the Hydra lies ujjon one side, and uses two tubei'cles
as large, lobate, jJseudopodial processes which give a creeping motion to the creature.
Every one who has watched Hydra in aquaria has probably seen it creep or glide
slowly over the surface of a leaf or of the glass. It kee^js its normal position, attached
by the foot-disk, but glides slowly, and with a very uniform motion, over the surface
to which it is attached ; much as a snail creeps, only with a much slower movement.
This power of changing place is due to the cells in the foot-disk. Watching under
a microscope, this part of Hydra, when it is in motion, it will be found that the
external cells throw out pseudopodial processes, which extend in the direction in which
the animal is travelling ; so that Hydra can move by pseudopodia as truly as Amoeba
does. In the position which Hydra so often assumes, that of complete expansion
with the tentacles extended to their utmost, and forming a very large circle, its
chances for getting food in the well-populated, often semi-stagnant waters in which
it is so frequently found, are very great. Any luckless crustacean of small size, such
as Cypris or Daphrda, that happens to strike against one of those delicate tentacles
is pretty sure to be used as food by the Hydra. The tentacle against which the crus-
tacean has touched, curls around him, and after a few struggles his limbs fall power-
less, and he acts as though it had been paralyzed.

This peculiar paralyzing or stupefying effect is caused by the action of certain sting-
ing or cnidocells (also called lasso-cells), which are most abundant in the tentacles,
but are also found in otlier parts of the body. Each one consists of a comparatively

large body-part, from which stretch away interiorly
one or more slender protojdasmic processes to con-
nect with a deeper layer of the body-wall ; on the
outer end of the cell is usually found a small proto-
jilasmic process which jirojects into the surrounding
water, but is too small to be seen with the unaided
eye ; this latter process is termed a cnidocil, and
probably receives and conveys stimuli from the ex-
ternal objects to the cnidocell ; within tlie body of
the cnidocell is the capsule, a more or less ovate
structure, consisting of an outer wall which is per-
fect and comj)lete, and an inner wall which is folded
in upon itself at one end to form a tube, wliich for a very short distance is of some
considerable diameter, and then decreases in size and forms a long, thread-like tube,
coiled up in the cavity of the capsule ; within the larger, shorter part of this tube,
attached to its wall, are a number of recurved hook-like processes which vary in

Fig. 64 — .-), (MiiiloceUsof Tiihularia larynx;
Ji, ciiidoceUs of Hydra viridis.

HYDRO IDS.

75

number, shape, and position in different species ; the remainder of the cavity of the
capsule is filled with a liquid very similar to, if not identical with, formic acid. Now,
when any stimulus brings a cnidocell into
activity, it forcibly ejects the larger part
of the tube by a process of evagination or
a turning of this part of the tube inside
out, as one turns the finger of a glove ;
this movement is quickly followed by the
ejection of the smaller part of the tube in
the same manner, by evagination. If the
body of some animal has touched
the cnidocil, then that body is pene-
trated by the thread-like tube, and
also possibly by a portion of the
larger tube with its recurved
hooks, and then the formic
acid of the capsule pours
into the tissues of the i»rey
and produces the general
paralysis above mentioned.
This paralysis, of course, is
not the effect of the formic
acid from one capsule, but
from many. Once used, the
capsule is useless, as the tube
cannot be withdrawn into it
again.

Other tentacles also close
around the prey, and by
their combined action it is
conveyed through the mouth
into the genei-al cavity; here it may be seen, with microscopic aid, to break down and
go to pieces, the products of the disintegration being a fluid, evidently a nutritive one,
whicli then flows to all parts of the body, and the remnants of the liard chitinous skele-
ton wliich are ejected by the mouth or through an opening which may be extemporized
anywhere in the wall of tlie proboscis. This form of Hydra in wliich it is unconnected
with any other individual or zooid is termed the solitary condition.

When tlie surroundings are favorable for its vegetative life, one usually may find
one or more Hijdroi attached to the body of what appears to be a main stem or parent
form. These attached or appended zooids have been produced by a process of bud-
ding from the parent individual, and each one of them ultimately separates from its
parent by a constriction at its base and becomes a free and independent solitary
Hydra. A bud starts as a small, rounded swelling on the side of the body ; the swell-
ing being hollow, and its cavity being directly continuous with the general body-cavity
of the parent ; by ordinary growth it attains considerable size, and from its distal end
a number of small swellings or prominences appear, wliich elongating, develojD into
tentacles ; the portion of the bud anterior or distal to the tentacles becomes the pro-
boscis or hypostome, and a mouth is formed in its distal end. Being structurally com-

FiG. 65. — Diagrams of cnidocells; A, previous to emission of contents ; B,
first stage of emission; C, filament completely extended; a, wall of
capsule; h, barbed sac; c, filament.

76

LOWER INVERTEBRATES.

im^

■ n

plete, it catches and digests food, and performs all its functions while still attached to
its parent. After a time a constriction separates it from its parent, but tlie opening at
its base never entirely closes (at least in some species), and is
known as the porus abdominalis. It does not fmiction as an
anus, however, and cannot be so considered. Before the first
bud is set free, a second one may appear, and even a third and
fourth on the parent body. Moreover, a secondary bud may
appear on the body of the first bud, a tertiaiy on the body of
tlie second, and a fourth on the body of the third before the
first bud has become free. This is known as the compound or
colonial condition.

Another method of increase whicli rarely occurs in Hydra
is division or fission, in which the entire animal divides into
two parts, each develoj)ing .all the p.arts necessary to make it a
complete Hydra. Trembloy observed this method, Rosel also
witnessed it, and Marshall has seen three cases of it. In this
comitry the process has been seen by Mr. T. B. Jennings, of
Sjiringtield, 111. The wonderful power which Hydra possesses
of reproducing lost parts was first discovered and made known
by Trembley, of Geneva, in the first half of the eighteenth cen-
tury. He determined that even a small piece of Hydra vulgaris
possesses the power, under favorable conditions, of develo]iing
into a perfect animal. His erxperiments were very varied, and
many of them have been often repeated with the same results,
since his day. Baker repeated nearly all
of them. The most remarkable of his
experiments in this line, was the turning
of the hollow, cylindrical body of a Hydra
inside out ; so that the inner layer which
before did the digesting, now performed
the functions of the cuticle, and vice
versa. This experiment, which requires
very skilful manipulation, has been, I
believe, repeated but by one biologist.
Professor Mitsukuri, of the University
of Tokio, Japan.

In a limited region on the body of Hydra., just below the
tentacles, there appear under certain conditions, small out-
growths of the body-wall which prove to be the spermarics;
in them being developed the spermatozoa. Lower down on the
body, in another limited zone, larger, rounded swellings are
enlarged; d.tentades; c, (Jeyeloped, which are the ovaries. Just how fertilization is

Dody cavity; e, ectoderm; Ji '

n, eiidoderm; m, mouth; accomplished is unknown, but the esi;g having been fertilized

s, supporting lamella. ^ ' ."-^ ii i '

passes through a morula st.age in which the outer cells become
prismatic, forming a definite membrane around the interior; a chitinous coat is devel-
oped .about it, and then there occurs a retrograde step, as the entire embryo fuses into
a simple, non-cellular mass ; within this mass a small cavity appears, the first formation
of the body cavity. In this condition it remains quiescent for a time, and then the

Fig. 67. — Transvt^rse section
of Hiidra, greatly en-
larged; letters as in fig.
66.

Fig. 66. — Longitudinal sec-
tion of Hi/ili-a, greatly

HYDRO IDS. 11

outer shell breaking away, the embryo, still with a delicate shell around it, escajses into
the water ; a cleft appears in the body-wall, which becomes the mouth ; the tentacles
are developed, and the embryo bursting its thin shell, appeai-s as a young Hydra. The
development of Hydra is thus seen to be simple and continuous ; there are no great
or sudden changes such as occur in the life-histories of so many other animals.

There are a number of so-called species of Hydra found in the United States, the
most common of which are a green one known as Hydra viridis, and a light-brown one
called Hydra fusca. Tlie latter often attains a much larger size than the former, and
on account of its being much more translucent, is a better kind for study. They are
found in slow or stagnant water, and are sometimes so very alnmdant as to form a
delicate, fringe-like covering over every submerged object, in quite a large pool.
Hydra has also been found once in a brackish arm of the sea in Germany, by Marshall.
Having obtained a general idea of one hydroid, we may now take up the systematic
arrangement of the group, considering the various sub-orders and a few of the most
prominent families.

Sub-Okder I. — Eleutheroblastba.

This, the lowest sub-order, has for its type the genus Hydra, which has already been
described at length. No other genus belonging to this group is known. This sul>
order is destitute of a hardened body-envelope, and the zooids of the body, or troph-
osome, are never firmly attached. Even more simple than Hydra is the peculiar genus
Protoliydra found by Greef in the ocean at Ostend, Belgium. It can be best described
by saying that it closely resembles Hydra, except that it entirely lacks the tentacles so
prominent in that form. It reproduces by transverse fission. So little is known of
the structure and growth of Protoliydra that the position which it is made to occujiy
in our classification must be regarded as provisional.

Sub-Okder II. — Gyiotoblastea.

. All the members of this division have a Jiardened body-envelope called the perisarc,
and live in colonies whifh are always attached to some foreign support. From the
next division of the same rank, they are separated by never having the reproductive
and nutritive portions enclosed in a chitinous capsule, and the generative zooids do not
usually become free, independently developing organisms. The generative zooid, escaped
from its parent, may have a medusa form, from which ultimately a large number of ova
are dropped, or it may assume the condition called the actinula, an oval body floating
passively about or creeping on the bottom. In those hydroids which h.ave an actinula
this body develops directly, without intermediate metamorphosis, into a hydroid of
the same form as that from which it sprung. In some of the gymnoblastic hydroids
there are no free medusw and no actinula, i)roperly so called, but a locomotive zooid,
called a sporosac, which performs the same function. The sporosac is a ciliated body,
capable of active locomotion, and possessed of two tentacles. It carries in its cavity
a single ovum. In many of the young gymnoblastic hydroids, the embryo leaves the
mother's care as a planula, which develops directly into a hydi'oid similar to that from
which it originated.

"With this sub-order a new feature is introduced. In Hydra we found the nutritive
and reproductive systems united in the same individual, but here we find certain por-

78

LOWER INVERTEBRATES.

Fig . GS. — Development of Eudendrium ; a, free-swimming planula; h, about to be
attached; c, d^ attached; e, beginning of hydi'orhiza and hydrauth.

tions of the colony set apart for the capture and digestion of food, while other portions
have for their only function the perpetuation of the sjiecies. It must be remembered
that the following account is a general one, and that there are many exceptions to it,
some of which will be subsequently mentioned.

We can best understand the structure of a colony by following it briefly in its
development. From the egg there hatches out an elongated young, known as a plan-
ula, which freely swims
by means of the cilia
^\ith which the sur-
face is covered. This
finally attaches itself
to some submerged ob-
ject, loses its cilia and
begins to develop the
true liydroid condition.
Around the upper
(free) end appear the
rudiments of the ten-
tacles, while the base
begins to divide up and
send out processes.
These latter grow and ramify in a manner strikingly like that of the roots of a tree, and
produce what is teclinically known as the hydrorhiza. From this root-like portion other
individuals or zooids develof), some of whicli are like the first, and from their greater
or less resemblance to flowers, are called hydranths. These liydranths form the nutri-
tive portions of the colony. They may be either stalked or sessile upon tlie hydrorhiza.
Other zooids are also developed from the hydrorhiza or from the hydranth itself,
but these never possess the tentacles and digestive organs of the hydranths, but
have only reproductive functions, and are called gonangia. In these latter are devel-
oped small zooids which in some cases become free, in others they never separate from
the parent. These medus£e or medusa-buds develop the male and female elements
(eggs and spermatozoa) which in turn produce other colonies similar to that de-
scribed.

Here some very interesting questions arise, the most prominent of which is wliat
constitutes an individual ? From a single egg there is developed a number of zooids
from which there escape quantities of medusae, which are frequently capable of feeding
and of reproduction. Are each of these jelly fishes, reproductive sacs, and feeding
portions to be regarded as separate individuals or as parts of one individual ? The
latter is the true course ; an individual eml)races all the jiroducts of a single egg,
and the name zooid is applied to the various more or less independent portions,
which, whatever their form may be, arise by budding or fission, but never by a new
ovarian reproduction. Tliis distinction is somewhat different from that found in tlie
sponges.

In a number of places in Europe and America, there has been found, besides Hydra,
another hydroid, living in fresh or brackisli waters, known as Cordylophora lacustris.
It is a compound form, attaining a length of two inches in good s]iecimens, and is
usually attached to some water-weed or to the stones in the bottom of a stream. I
have seen it flourishing in a stream where the current is very swift. Again it has been

HYDROIDS.

79

Fig. 69. — Cordijlophora Uicusfrls.

found in an old well. These two, Hydra and Cordylophora^ are the only hydroids

known to live in fresh-water. A third, imperfectly known form, allied to Cordijlo-

jyhora, has been described by Professor Cope, from a

lake in Oregon.

In the oceans, hydroids are very abundant, and

there are at least several hundred species. All of

them may be arranged in a few groups, most of which

are represented on our shores. Our first example of

the marine forms will be Clava lejytostyla, a beautiful

reddish species which occurs on our coast from Long

Island Sound northward. Its most common habitat

is at or near low water mark, attached to the rock-
weed (jFucks), where it forms colonies consisting of

numerous individuals attached to a common rhizome

or branching base. It is about a half of an inch in

length, and the " head " bears from fifteen to thirty

irregularly arranged slender tentacles. Beneath the

tentacles, at the breeding season, the small reproduc-
tive buds are arranged in groups as shown in the figure.

The re2:(roduction is essentially like that of the next

species. One of the most common forms found in shal-
low water (one to twenty fathoms) frouiVincyard Sound

n(_)rthward, is known as Eudendrium dispcir. It grows in colonies
from two to nearly four inches in length, and the jiarts of the
colony which correspond in appearance to the stems and branches
of a plant are dark-brown or black. At the tip of each branch
and branchlet is a hydra-like animal, or zooid, which is directly
connected with every other one in the colony, for the whole
colony is strictly comjiarable with a much-budded Hydra grown
to an equal height, and the general cavity of the body is con-
tinuous through all the stems and branches into every zooid.
When taken out of the water, however, Eudendriam retains
its shape, which Hydra cannot do. This stability or rigidity
is due to the existence of a nearly complete coat or covering
of horny material, chitin, which is secreted by the animal, and
which extends over all the colony, with the exception of the
zooids ; they remain unprotected. During the summer months
two kinds of Eudendrium may be found along the New Eng-
land coast, which are exactly alike in the characters given, but
differ in color, one having white zooids, the other yellow. A
little careful examination will show that upon the bodies of the
white zooids are a series of structures arranged in a circle just
beneath the tentacles ; each one of these is in shape like a short
string of beads, which are supposed to be male organs, showing
that the white colonies are male. The yellow ones are colored
by a number of simple bud-like processes which are irregularly

scattered on the body of the zooids ; they are the female reproductive organs or ovaries.

In Eudendrium then, the sexes are in different colonies. An egg having been fertil-

FiG. TO. — Clava leptostijla,
enlarged ; a, b, c, d, me-
dusa buds.

80

LOWER INVERTEBRATES.

ized, passes through the process of segmentation, a cavity appears within it, then it
assumes an elongated form, possesses a double wall about the central cavity, develojjs
cilia upon the outer surface, and breaking tlirougli the containing
wall, escapes into the water where it leads a free life for a brief
time (see Fig. 67). Before long it enlarges at one end, settles down,
becomes attached by its larger end, loses its cilia, and proceeds to
develop a new colony of Eudendrium in the following way : It en-
larges at its free or distal end, and around this enlargement appear
a number of smaller swellings which develoji into a wreath of ten-
tacles ; a mouth forms in the extremity of the proboscis and a layer
of chitin is secreted around the body. Then by the simple pro-
cesses of growth, combined with budding, a new colony is formed
quite like the one from which the germ came. ' In this case the
medusa buds do not develop into free-swimming jelly-fishes, but
discharge their reproductive elements without leaving the parent
colony.

Parypha crocea, a beautiful hydroid of a bright red or salmon
Fig. n.~Eudaidrium color, is very common along the whole New England coast, while
ma?e"^'cotony with a closely related, if not identical species, extends southward as far
me usoi u s. ^^ South Carolina. It attains a length, in favored localities, of five
or six inches, and grows in great luxuriance on the piles of wharves or
bridges, especially where the water is slightly brackish. The outer or
lower circle of tentacles are long, and just within them arise the medusae
buds resembling clusters of small, bright-red grapes. In each colony
the sexes arc distinct, and in these buds the eggs or spermatozoa are
developed. The young escape in the actinula condition, and creeji
about, finally attaching themselves, and then by budding and branch-
ing, large colonies are formed, which in turn jjroduce medusa buds,
thus completing the life cycle.

Another common form on our Atlantic coast from South Carolina
to the Gulf of Maine, is Pennaria tiarella. It grows in colonies equal
in size or a little larger than those of Eudendrium, and is found at-
tached to rocks and eel gi-ass, and often to floating algae. The zooids
are usually a roseate color, and the species is remarkable for its beauty.
In general structure Pennaria is like Eudendrium, but differs in hav-
ing, in addition to the one row of large tentacles, a number of smaller
capitate tentacles, arranged, more or less definitely in two circles near
the anterior end of the proboscis ; it also differs in its mode of branch-
ing, and in its method of reproduction. In the summer months there
may be found growing out of the lower part of the proboscis, one or
more oval bodies which finally develop a deep bell-shaped body with a
considerable opening at the free end, about which are a number of rudi-
mentary tentacles ; within the cavity of the bell-shaped zooid is a pro-
cess corresponding in shape and position with the clapper of a bell, it
is in fact the proboscis, and at its free end is the mouth. By means
of a sort of gullet or oesophagus passing through the proboscis, the
mouth communicates with the central digestive cavity located at the base of the pro-
}:)oscis in the upper part of the umbrella ; from this central cavity four ducts at four

Fig. 72. —Pari/jtlin
crocea, natural
size.

11 MM

■^ tiff W»'^ -^

Tubularia indivisa, tubulariau hydroid.

HYDRO IBS.

81

. equidistant points stretch away to the rim of tlie bell, where they are all connected by
a tube passing around the rim. By means of these gastrovascular canals nutritive mat-
ter from the stomach is carried all over the body. Stretching partly across the open-
ing into the bell, is a thin, centrally-perforated membrane called the velum or veil.
After one of these medusas has been completely developed on the proboscis of the
hydroid of Pennaria, it is freed from the proboscis by a constriction which cuts in two
the small peduncle by which it had been attached, and the medusa floats away free in the
water. It is not left to the mercy of currents, however, but is provided with a rather
peculiar locomotor apparatus. The cavity of the bell being filled with water, its mus-
cular walls are powerfully contracted, and the water being ejected from the oj^ening
in the velum, the medusa is forced through the water in the opiiosite direction ; then
expanding its bell by other muscles, it is ready to contract again and send itself still
farther on its waJ^ The tentacles and outer surface of the medusa are well supplied
with cnidocells with which they defend themselves and kill their prey in the same
manner as Hydra, and as the zooids in the hydroid colony. The medusas are sexual
zooids, the sexes being separate, and in the case of Pennaria, the male and female
elements are developed within the walls of the proboscis. From a fertilized egg a
planula is developed, which in turn gives rise to a hydroid colony of the Pennaria
kind. The life-cycle is thus more comj^licated than in Eudendritmi by the introduc-
tion of the medusa stage. The length of an average Pennaria medusa is about one-
sixteenth of an inch.

Objects of more exquisite beauty than some of these hydroid-medusag do not per-
haps exist. Each minute crystal chalice with its beautifully cur\'ed outline, elongated,
delicate tentacles gently coiling and uncoiling, and its slender proboscis which hangs
like a lamp in its centre, lighting it M'ith a soft phosphorescent
glow as it swims with most perfect grace at the surface of the
ocean, is the very type of delicate beauty, suggesting the won-
ders of fairy-land.

The dredge frequently lirings up delicate pink or flesh-colored
hydroids consisting of single stems, each supporting a single
hydranth. This hydranth bears two sets of arms, those around
the free end of the proboscis being much shorter than those nearer
the base. This form w-as called by Agassiz Corymorpha pendula.
It lives with the base imbedded in the mud, and grows to a
length of four inches. The investing envelope is very soft, and
the animal is able to greatly modify the shape of the stalk and pro-
boscis. The medusa buds never become free-swimming jelly-fishes,
while the hydroid stem always bears a single head or hydranth, a
fact which led Allnian to refer it to the genus 3Ionocaulis.

The genus Tahularia and the closely allied Thamnocnidia, are represented on our
coasts by several species. The hydranths are borne on slender stems, and form col-
onies reaching sometimes a height of eight or ten inches. Under a low power of the
microscope, the beauties of the animals stand revealed, far exceeding the power of any
pen to describe or brush to paint. The hydranth is surrounded with two circles of
tentacles, and from between the lower ones the reproductive zooids hang down like
bunches of grapes, or they cluster around the proboscis inside the outer circle of ten-
tacles, so that it requires no very vivid imagination to imagine the whole a delicate
fruit-dish filled with the most beautiful fruit. From these raceme-like clusters the
vor,. I. — 6 '

Monocaidistpen-
dula, natural size.

LOWER INVERTEBRATES.

young come forth in an netiimla condition, presenting distant resemblances to a jelly-
fisli. The body is long and surrounded by a single circle of tentacles. This larva
soon becomes attached and then develops into a form like the parent.

Many of the small s])iral shells found in the shallow salt-water just below the
water's edge, ai-e found to be inhabited by hermit crabs, which travel about very

actively by protruding their legs
from the apertm'e of the shell.
On the backs of many of these
shells is what appears to the
eye, a white, delicate, mossy
growtli, covering most all of the
shell, excepting that jjart which
drags on the bottom as the crab
travels. Under the microscope,
this mossy growth proves to
be a colony of very beautiful
hydroids named Ilydractinia.
They live in colonies, but in-
stead of forming a colony by
branching in the ordinary way,
the hydrorhiza, or part which
attaches the colony, spreads out
farther and farther, and sends uj)
more and more buds, each one
of which becomes a zooid, but
which does not bud and is not
covered by chitin. The hydro-
rhiza is covered by a layer of
chitin, and at irregular intervals
the chitin is developed into a
large projecting spine. The
zooids are very contractile, and
when withdrawn to their utmost,
the hard chitinous spines pro-
ject slightly beyond and protect
them. Examining carefully the
zooids of IL/dractinia it is found
that there are the ordinary feed-
ing zooids, the reproductive
zooids, male and female, and a
third kind which are destitute
of true tentacles, have very slender, much elongated bodies, and are powerfully
armed with strong batteries of cnidocells with which they perform their duty of
protecting the colony. From a fertilized egg of Ilydractinia is developed a planula,
which in time gives rise to a JL/dract'nua colony. There are a large number of
jelly-fishes known, which, from their structure, are classed among the Gymnoblastea,
although nothing is known of their attached hydroid condition, or even if they pass
through such a stage.

Fig. 74. — Hydractinia et'AiKaia, enlarged; a, nutritive, b, female
reproductive zooids.

I ^

5" ri

§ Q

^ O

HYDROIDS.

83

In the form known as Lizzia, it is the jelly-iish itself that produces the medusa
buds. In our iigure, which represents the young of X. octopunctata, may be seen
younger jelly-fishes budding from
tlie sides of the i^roboscis of the
parent, and frequently in life, one
can see still younger buds in these
embryos before they free themselves
from the parent. When arrived at
a moderate size, these buds begin
tlieir contractions and struggles
which finally end in their breaking-
loose from the parent, and the be-
ginning of life on their own account.
With age and increasing size, the
tentacles grow nuich longer, those
arising ojiposite the radial canals
being in bunches of five, while
those at the intermediate points
are in thi'ees, so that there are
thirty-two in all.

Here also belongs the genus Stomatoca, with its two long, marginal tentacles. In
confinement our >S'. apicata seems to prefer the bottom of the aquarium, and but rarclj-
comes to the surface.

Fig. 75. —Lizzia octopunctata, youug.

Sub-Okdek III. — Calyptoblastea.

Nearly all the many species of Hydroids on the American coast which have bell-
shaped hydrotheca;, belong to the large family Cajipaxulaeidj:. One of the finest
representatives in American waters of this family of hydroids is Obelia longissima.
It lives in shallow water, and down to a depth of about twenty fathoms, from Lontf
Island Sound to the Bay of Fundy. The colonies are often quite large, measuring
eight to twelve inches in length, and are of great beauty; at the tip of each stem
and branch is developed a zooid, and about the zooid is a cup of chitin, called
hydrotheca, into which the zooid may nearly or completely retract itself, and out
of wliich it may stretch and unfurl its single wreath of tentacles ; the rim of the
hydrotheca is cut into a number — twelve to si.vteen blunt teeth ; the proboscis is
very large and very mobile, constantly changing shape. In the axils of the branches
are developed other chitinous cujis (gonotheca?) larger and alwajs of a different shape
from the hydrothec.T, in each of which there is a long, simple zooid, destitute of mouth
and tentacles (a blastostyle) ; on its sides are produced small buds, from eighteen to
twenty-four, which develop into medusse. They are found escaping from the gono-
theca; from April to June.

These medusaj are sexual, and bear either male or female elements along the radial
canals ; each fertilized egg develops into a ciliated planula, and this gives rise to a col-
ony of Obelia longissima. One finds certain points of difference between this medusa
and that of Pennaria. The contracting wall which subserves the function of locomo-
tion is not bell-shaped, but is nearly a flat disk, and tentacles exist all round the edge
of the disk, there being from twenty to thirty, while the medusa of Pennaria has only

84

LOWER INVERTEBRATES.

four rudimentary ones. On the edge of the disk, at equidistant points, are a number
of globular bodies containing a cavity in which is a bristly ridge, and which is nearly
filled with a clear liquid, in which are a few small calcareous particles that strike
against the bristles when any disturbance in the water outside sets the liquid of the sac
in motion. These are known as otocysts, and are supposed to be auditory organs.
The medusre of Obella longissima are very minute, measuring only one-sixtieth of au
inch across the disk, and one-fortieth across the outstretched tentacles.

Fig. 70. — Canipanularian hydroid; ((, 6, hydranths; c, liydrorliiza; /, gonangiuni; jy, medusa.

A less conspicuous but very beautiful hydroid of special interest, and belonging to
the same family as Ohelia, is represented by several s]iecies on the New England
coast. They belong to the genus Gonotliyrea., and, at a hasty glance, look like dimin-
utive or young specimens of Ohelia. In height tliey do not exceed an inch and a half
or two inches ; the hydrothecse in the most common species, G. hycdina, are long, of
very thin texture, and the rim is cut into numerous shallow teeth of castellated form.
The gonothecse spring from the axils of the branches, and contain a blastostyle upon
which are formed a number of buds that develop in regular sequence from above
downward ; when the uppermost one is fully grown, it pushes out of the toji of the

HYDROIDS.

85

gonotheca, but still remains attached to the blastostyle by a slender peduncle ; this
zooid is now seen to be sexual, and contains within the walls of its proboscis, the
sexual elements ;
the outline is nearly
S])herical, being cut
off at the farther
end where there is
an opening into the
cavity of the zooid ;
about this opening
is a wreath of ten-
tacles, and pendent
in the cavity of the
bell is a proboscis
destitute of a
mouth ; the cavity
of the blastostyle is directly contin-
uous with a central cavity in tliis
meconidiuni, as this kind of zooid is
termed, and from this central cavity
four radial canals pass out to four
equidistant points on the edge or rim
of the bell, where they all join a cir-
cular canal ; these meconidia never be-
come free, but after discharging their
contents, they die and disintegrate.
The fertilized eggs develop into cii
ated planulse which finally form col-
onies of Gonothyrea hi/alina.

These meconidfe which are evi-
dently medus£B that never become
fi'ce, are of great interest, being, in all
probability, degenerate forms.

Another large family, the Sertu-
LAEiD.E, belonging to this same group,
is represented in America by a beauti-
ful species, Sertularia argentea., so-
called from its light silvery color.
The colonies are often a foot in height,
and the shoots usually grow in clusters;
the branches ha\-e a subverticillate ar-
rangement, giving the colony an arbor-
escent a]ipearance. If a small ]iortion
of a colony be examined with a magni-
fier one discovers very peculiar hydro-
theca', which are very differently ar-
r;niged from any described above ; they are nearly tubular, somewhat narrowed at the
toj), with jjointed lips, and are either free or set into the sides of the stems and branches.

Fjg. 77. — Gonotheca witb mecoiiidiaof GoiiQth;irca ; h, blasto-
style; (f, gonophores in various stages of development;
(?, meconidia; m, ovuui; o, embryos.

86

LOWER INVERTEBRATES.

The gonothecsB are developed on the branches and are elongated, somewhat nrii-
shaped, aperture central, termii.al with usually two, occasionally one long horn at the

anterior end. The eggs are partly devel-
oped within the gonotheca, and then pass
into a sac which projects from the orifice
of the gonophore, where they finally be-
come planula; ; these after living a free
life become attached and form a new col-
ony. Sertularia argentea is found from
the New Jersey coast to the Arctic Ocean
from low-water mark to a depth of over
one hundred fathoms. It is very widely
distributed, being found on both sides
of the Atlantic and on the Pacific shore
of the United States. Like many other
Hydroids it is often col-
lected as sea-moss and is
not infrequently seen at
the florists for decorative
purposes.

Another very common
species of Sertularia is
/S'. pumila, a very much
smaller liydroid, not over
one inch and a half long,
and often found in abun-
dance on the common
Fucus or d:irk brown
rock-weed. The liydro-
thecaj are opposite one
another on the stem, giv-
ing it a compactness of
structure and regularity of outline not

The colonies

_^^^^^ possessed by S. argentea.

^^*^°'^-'* are sexually perfect from May to Sep-
tember on the New England coast. 1 lie
method of reproduction is very similar to that of 8. argentea.

A third large family corajsrises the feathery forms known as the Plumixarid.e.
They are represented on the New England coast by Plumularia tenella, Plmmdaria
verrillii, and Aglaophenia arborea ; the last species was described by Desor in 1848,
and has, I believe, never been found since. Other species of Aglaophenia and Plum-
ularia ai'e found on the Carolina coast, and still others in the Californian waters.
Perhaps the most elegant in apjicarance of all the American hydroids is the ostrich
jilume of our Pacific coast, AglaoplLenia struthionidcs. It varies much in size and
color, but always retains the appearance of a diminutive ostrich feather. Microscopic
study shows that the hydrotheca^ are arranged in a single row on one side of each
branch or pinna, and that tlie branch is divided into very short joints, one to each
hydrotheca. Each hydrotheca has its rim ornamented with a number of sharjily

Fig. 79. — A frag-
ment of Sertu-
hiria. enlarged,
showing the cups
or liydrotheca.

HTDROIDS.

1. Pennaria tiarella. 2. P. tiarella, enlarged. 3. AgJaophenia stmthionides. 4. Eudendrium

dispar, male, enlarged.

HYDROIDS.

87

^a

k

M

.^r

'V

pointed teeth, and three minute tubular processes are disposed about its mouth, one
on each side and one on the outer or anterior surface. These processes are termed
iicmatophores, are tilled with processes of the body substance,
and in structure and dcvelojiment are believed by Ilaniann
to give evidence of being degenerate zooids. Certain of the
branches or piinnai are at times replaced by cylindrical struc-
tures which are covered with rows of nematophores, and are
the cups or baskets in whifh the generative zooids are devel-
oped ; they are termed corbul;i>, and in some genera are mcta-
morjihosed branches, while in others they are modified jiinna'.
A pinna is smaller than a branch, and differs from it in the
character of the zooids formed upon it. The egg develoj)S
into a planula, which becoming attached forms a new hydroid
colony.

These three great families, represented here by the genera
Sertularia, Obelia, GonotJq/rect., and Aglaoplienia., are all mem-
bers of a sub-order of hydroids distinguished by having the
hydranths surrounded by chitinous cu2)s, and the jsossession rvg^-i
of longitudinal ridges in the body ca\ity. This group lias ^ (\^
been variously termed Thecata l)y Ilincks, Calyptoblastea by
Allman, and Intajniolata by Ilamann.

As among the Gymnoblastea, we find here medusa? which
agree in structure with those which are undoubtedly calyptu-
blastic, but of whose early development we know nothing.
We can mention but one example. One of our larger jell)--
fishes is Zijgodactijla [/roidandica, which sometimes acquires
a diameter of even eleven inches. In color it is a light violet,
with numerous brownish reproductive organs. The numerous
tentacles which fringe the margin of the umbrella lianu' down
a yard or more when fully extended. Concerning the habits
of these animals Mrs. Agassiz has written: — "The motion of
these jelly-fishes is very slow and sluggish. Like all of their
kind, they move by the alternate dilation and contraction of
the disk, but in the Zygodactijla these undulations have a

certain graceful
indolence, very
unlike the more
r a p id mo v e-
ments of many

of the medus;i='. It often remains quite
motionless for a long time and then, if
you try to excite it by disturbing the
water in the tank, or by touching it, it
heaves a slow, lazy sigh, with the whole
FIG. SI. - z,„io,i„riiiia iironiamuca. ''O'l}' '"'si'iS slowly as it docs SO, and then

rela])ses into its former inactivity. In-
deed, one cannot hel]i being reminded, when watching the v.ariety in the motions of
the different kinds of jelly-fishes, of the difference in temperament in human beings.

'^a/-

iiif

Zijdoihtrtijla (jronlandlca.

Fia.80. — Co^bulaof.<///tfn-
y;/(t /((« struthionidts, enlarged.

88 LOWER INVERTEBRATES.

There are the alert and active ones, ever on the watch, ready to seize the opportunity
as it comes, but missing it sometimes from too great impatience ; and the slow, steady
people, with very regular movements, not so quick perha])s, but as successful in the
long run ; and the dreamy, indolent characters, of which the Ztjgodacti/la is one,
always floating languidly about, and rarely surprised into any sudden or abrupt
expression."

Nothing is known of the develojiment of this form, as all attempts to raise the
eggs have proved futile, and it is unknown whether it has a hydroid stage or not.

Sub-Oeder IV. — Trachymedus^e.

The Trachymedusre are usually considered a distinct group of Hydroidea, espe-
cially characterized by having a direct development ; that is, they are jelly-fish, which,

in general structure, ai-e like the medusas de-
velo])ed from hydroid colonies, but their eggs
develop directly into new medusas, and not into
hydroids. They have then no hydroid state.
They are i-epresented in our waters by a num-
ber of sjjecies, among them Trachynema digi-
tale. The full-grown medusre of this species are
from an inch to an inch and a half in length,
the walls are very thin, and not much used for
locomotion ; the latter function being performed
principally by the muscular velum which pushes
itself outward with considerable force. The
proboscis is very large and has four lip-like ex-
pansions about the mouth ; the tentacles are
numerous, and four garnet-colored otocysts are
present at equidistant points on the margin of
the bell. The ovaries develop from the upper
parts of the radial canals, are cylindrical and
much elongated, hanging pendent in the bell,
and reaching nearly to the velum.

Cunina, another genus of this grouji, though
not so common as Trachynema., is not rare on our coasts, where it is represented by two
S]jecies, C. octonaria and C. discoides. An interesting fact in connection with these
forms is that they live on Turritopsis, a jelly-fish allied to the Stomatoca mentioned on
a jjreceding page.

Sub-Order V. — Hybrocorallin-e.

Among the many creatures that contribute to the building of a coral reef, are to be
counted certain hydroids. For many years there was no suspicion but that the Mille-
pore corals were built by true coral polyps. Pi-ofessor Agassiz disco\-ered their true
nature twenty-five years ago. Latei-, some other coral-making hydi-oids have been
thoroughly studied by Professor Moselcy, of Oxford, late of the "Challenger" expedi-
tion. They are A-ery beautiful forms, and there are three kinds of zooids ; the ordinary
feeding forms, the reproductive kind, and the dactylozooids. The latter have no
mouth and gastric cavity, and i)Ossess only a tentacular function.

Fig. 82. — Trachynema (hr/itale.

JELLY-FISHES. 89

These foi'ins, represented on our southern coasts by Millepora alcicornis, form a
coral wliicli, however, is composed of calcareous fibres and is traversed in all directions
by canals. The little cups occupied by the polyps are shallow, but as one polyp dies
another succeeds it, forming a jiiartition separating the new cup from the old, so that
in time the pits of the coral become deep but are divided up by a series of transverse
partitions. A similar structure exists in some of the true corals.

Among the fossil forms referred to, the hydroids, the Graptolites of the Silurian
period are most 2)romiuent. In these forms we have an approximation in general
apjjearance to the Sertularian. These, so far as we are able to discover their anatomy,
consisted of a narrow tube bearing, on one or both sides, a series of hollow teeth,
through which the tube communicates with the exterior. It
is supposed that each of these teeth was occupied by a zooid
similar to that found in Sertularia or Plunutlaria. Haeckel ■'j:'-^-^
has described, from the lithographic stone of Solenhofeu fig. 83. — Porii.ni ..ni uiapto-

^ ^ lite, enlarged,

(Jurassic age), two fossil medusse, which he refers to the

Trachymedusa^ and from later beds portions of the incrusting hydrorhiza of Hydmc-
tinia have been found, and true Sertularians occur in the pleistocene of England.
Other forms referred with more or less doubt to this group occur in the Cambrian,
carboniferous, etc.

Samuel F. Claeke.

Oedee II. — DISCOPHORA.

Among the Meduste ^^■hicll attain the greatest size and probably are the most
commonly observed are those called the Discophora, "sea-nettles," "sea-blubs," or
"jelly-fishes." The members of this group are very characteristic, and are named
from the disk-shaped outline of their bodies. Although the group of Discophora
is not a large one, there being barely a half dozen genera found in our waters, it
presents some of the most interesting features of all the known Medusas.

The bodies of all the jelly-fishes are \-ery gelatinous, composed for the most part
of water, and when taken from their native element sjjcedily melt away, leaving a
tliin film behind. Although these animals are not the only ones which have gelatinous
bodies, they excel all in the amount of fluid in their tissues, and are consequently
among the most transparent of animals.

The habits of the Discophora are very curious. Many swim at or near the surface,
sometimes protruding their bodies a little out of the water. Some are confined to the
deej) seas and are drifted only by accident into shallow waters. A rough sea sends
many below the reach of the agitated waters, and in a calm they rise to the surface,
to come into the range of the sun's rays. Whatever their purpose is in this latter
habit, we may trace to it the name of " sun-fish," which they bear in some localities.
Most of these animals in their adult conditioii are free swimming, while many are
attached to the ground in their younger stages of growth in a way which will be
treated of in our account of the development. Oassiopea is attached in the adult
state in the following jieculiar manner. This genu:; is very common along the Florida
reefs where, instead of swimming about in the water, it lies at the bottom on the coral
sand, lazily flapping its disk in a monotonous manner. It is not firmly anchored to the
bottom, yet rarely changes its position any considerable distance.

90 LOWER INVERTEBRATES.

Probably all are marine and many genera gregarious, either seeking each other's
company, or huddled together by ocean currents or tide eddies.

At spawning-time they are said to don brighter colors, or at least their ovaries and
spermaries at that time become more highly colored. Like the hydroids, their
organs for defence and offence are the stinging-cells by which their bodies are covered.
Many sting with great violence, while others can be handled with hnpunity. None,
however, are destitute of stinging-cells.

All are phosphorescent, especially when irritated, while the color and intensity
of the emitted light varies witli the genus.

One of the most common Discophores in New England waters is called Ci/anea, and
is a representative of a family of moderate size known as the Cyaked^. The most
striking peculiarity of Cijanea is its disk-shaped body, wliicli varies in size from that
of a penny to several feet in diameter. Its color is reddish brown, but when dead and
washed about for some time it becomes light blue. The body-disk is divided into two
well-marked regions, called the aboral and the oral, or the upper and lower surfaces
as the animal naturally swims in the water. Tlie upper surface is smooth and without
appeiKhiges, save little filaments which are remnants of bodies of considerable
size in the young of the animal. The under or oral surface is so called from the fact
that from it hangs not only the stomach with its mouth, but also many other important
structures. Tlie thickness of the disk in its centre is much greater than at the
iieripherj', where it becomes very thin and flexible, and capable of considerable motion.
Around the margin of the bell are found at I'egular intervals eight sense-bodies, which
lie in deep incisions in the rim. Each sense-body is a small sac or cyst mounted on a
sh(irt peduncle, and in the interior there are a number of rhombohedral otoliths of
calcnreous composition. Each sense-body is covered by a thin, gelatinous wall stretched
above it, which is known as the "hood." From the existence of this hood in the
Discophora, and its absence in the Ilydroidea, Siphonophora, and a few other jelly-
fishes, these animals are called the hooded-eyed medusii?, while the latter are sometimes,
especially in older writings, designated the naked-eyed jelly-fishes.

The most prominent of the several appendages which hang from the oral surface
of the disk is a thin, curtain-like body of great breadth, which is thrown into a great
number of folds and frills. This curtain is open below, and its inner walls make the
walls of tlie stomach. It hangs far down below the oral surface of the bell, extending
far beyond it as the medusa, by strokes of the margin of the disk, is driven along
through the water.

The tentacles of Cyanea are found in bundles, in each of which there is a great
number of these organs. Each tentacle is long, thread-like, and very contractile,

possessing stinging cells which, however,
are rathei' feeble in their action in the genus
Cijunea. The tentacles in larger specimens
of tlie genus reach an extraordinary length,
nnd, as in other Discophora, have for their
function the capture of the food.

The genus Aio-eJin, the type of the
, , J .,, familv Ai'RELiiD.E, is, next to ( V?«e«, one

of the most common representatives of
the Discophora in New England waters. Although it never reaches the great size
attained Ity the former, it may well be ranke<l ns one of the largest of our Acale]ihs.

It-

f

^^«3>

iy^

JELLY-FISHES. 91

The body of Aurelia, like that of Ci/anea, is disk-shaped, but has a creamy-white color.
There are in this genus as in the last, eight marginal sense-bodies, each covered by a
hood to which i-eference has already been made. A great difference between the two
genera is in the development of the aj)peiidages to the oral side of the body, and instead
of there being eight clusters or bundles of tentacles as in Ci/anea, there is in Anrelia a
simple continuous circle of short filaments set around the disk-margin. Tlie tentacles
are relatively much smaller than those of Cijanea.

One of the most important characteristics of Aurelia is to be found in the structure
of the moutli and oral appendages. Instead of a curtain hanging down from the
middle of the disk, the mouth of Aurelia is formed in the following manner. From
the central region of the oral surface of the disk the oral appendages are suspended
by four gelatinous pillars. Between each pair of these pillars there is a circular
opening which communicates with a central cavity in which the sexual organs
lie. Below the sexual openings the pillars fuse, forming a gelatinous ring surrounding
the mouth and serving as a basis of attachment for certain organs, developments of the
lips, called the oral tentacles. These oral tentacles are four in munber, and are
commonly carried extended radially from a central mouth-oiiening. Each oral
tentacle has no resemblance to a m.arginal tentacle such as is found on the edge of
the disk in Ci/anea or Aurelia, but is short and thick, smooth above, and bearing on
its under side a deep groove which extends the whole length of tlie oral arm from
its distal tip to the central mouth. On the ridges which enclose this groove are
found at intervals peculiar, small, suctatorial mouths. The entrance to the stomach or
the large mouth in Aurelia is centrally placed on the oral side of the disk, and
communicates directly with a disk-sha]ied cavity, the stomach, which lies directly
above it. The lower floor of the stomach is formed by the oral surface of the bell,
a muscular layer, from which the four cylindrical bodies wliich support the oral
gelatinous ring are suspended. The roof of the stomach, or the gelatinous wall of the
bell, IS continued just above the mouth into a pyramidal jolly-liko projection, which,
however, does not protrude outside the mouth-opening.

The marginal sense-bodies of Aurelia are accompanied on either side by a gelatinous
extension or lappet Avhicli extends outward and hangs slightly do\^•nward. On the
.aboral surface of the Ijell, in the neigliborhood of the hood which covers the sense-body,
there is a raised circular area of doubtful function which is not found in the vicinity
of the sense-organs in Cijanea. This disk is called the siimespolster, and is, as its
name signifies, probably an organ of sensation.

Of the many extraordinary genera of Discophoi-ous medusa', one of the most
peculiar is the genus Cassiopea, especi.ally a species called C.fromlosa found about the
Florida Keys. This we may consider as the type of the family Cassiopeid^. Apart
from its curious habitat, being attached to the coral mud as has been mentioned above,
it is remarkable in the peculiar arrangement of the complicated oral ap]5endnges which,
although differing greatly from similar organs in the two genera already mentioned,
are typical of several of genera belonging to the same great group.

Cas&iopea frondosa is found lying upon its aboral surface on the nuid near coral
islands in Florida and elsewhere in tropical seas. As one floats in a boat over these
curious jelly-fishes, they look very similar to an algous growth on the sea-bottom, and
are easily confounded with some of the forms of corallines which abound on the neigh-
boring sheltered submarine banks. If, however, the medusa be closely scanned, it will
be found to move portions of its body voluntarilj-, and a throbbing or vibration, espec-

92 LOWER INVERTEBRATES.

i.ally of the edges of its disk, can be plainly seen. Although fastened to the ground,
it still keeps up a flapping motion of its bell ])robably for purposes of breathing, just
as is the case with free-swimming animals of closely allied genera.

One of the functions of the marginal tentacles of the Discophora is the capture of
the food. Tiie)' wind themselves about their i>rey, sting it to death, and then, by con-
traction, draw it to the mouth. lu a medusa which is fastened to the ground, tentacles
would seem to be necessary if the food was large and capable of movement. The con-
struction of the mouth of Cassiojxa shows that its food is of very small size. The
medusa feeds upon the animal and plant life which drifts past it, or which is caused to
move o\'er it by the slow flapping of the bell margin. It is therefore evident that ten-
tacles would be of little service to an animal with this mode of life, and accordingly we
find its bell margin is wholly destitute of those filaments called tentacles, which form
such a prominent feature in the adults of Cyanea^ Aurelia, and several other genera.

Throughout the animal world there are several examples which might be cited of
animals which uj)on becoming attached to the ground, after a free larval existence,
having no use for well-developed sense organs, lose the same or suffer a degenei'ation
in their complication. This can well be illustrated in the development of some well-
known genera of Ascidians, where the free larva has higher affinities throughout than
the adult, and where a highly-developed organ of sense is formed in a larva to be lost
in the fully-grown animal. The organs of sensation on the margin of the bell in Cas-
siopea are, however, as highly developed as in any of its relatives which swim freely in
the water. Abnormal as its mode of life is, the otocysts, or organs of sensation, found
on the rim of the bell, have not disappeared, neither has their number diminished.
In Casstopea there are sixteen of these bodies in normal specimens, and we also often
find monstrosities by which this number is increased to eighteen. Professor Agassiz
found twehe of these structures in Folyclonia, a closely related or identical genus.

The structure of the mouth of Cassiopea is somewhat as follows : In the centre of
the oral surface of the bell there is a gelatinous cylinder in which there is a central
cavity, but no external opening, in a position which corresponds to the mouth of other
Discophora. On the side of this cylinder, however, there are openings, four in num-
ber, leading into as many cavities partitioned by a thin membrane from the main
cavity in which the sexual products are formed, and perhaj)S through which they pass
when mature. From the oral cylinder there arise eight long arms which are commonly
extended at right angles to the cylinder jiarallel with the lower floor or aboral side of
the bell. Their ti])s extend a little beyond the bell margin, while the side adjoining
the bell is smooth. Each appendage is branched, and from its aboral surface there is
formed a great number of curious a])peudages of various functions. Two kinds of
ajipendages can be recognized. The former are simply little feeding mouths sur-
rounded by a circle of tentacles and resembling little Ilydne. Of these there are a
large number on the oral a])pendages, and each and all open into a system of vessels
which i)ass through the a]i])endages, and tiltimately ]wur their contents into the cen-
tral ca\ity of the oral cjlindei-. All of these Hydrm together make up the mouth of the
medusa, for they are the orifices through which food is taken into the stomach. The
second prominent appendages to the oral arms are small, flask-shajied, and o\()i(l
bodies, Avith a central cavity which oi>ens into the vessels jiaissing through the arms.
Tliey are, however, without an opening into the external water, and their true func-
tion is not yet definitely known.

A most interesting family, the Pelagid,k, is rejiresented in our waters by two
genera called Pdagia and Dactylometra. In Pelagia we have a si^herical-shajied

JELLY-FISHES.

93

medusa of pinkish color and eight marginal sense bodies, alternating with as many ten-
tacles on the bell margin. From the under side of the bell the oral appendages hang
far outside of the bell cavity, resembling in many particulars the oral tentacles of the
fcnus Aurelia. Pelagia is not a large medusa, and is very remarkable in its develop-
ment, as will be explained more at length later in our account of this part of the subject.
Dactylometra is closely allied to Pelagia., but has a larger number of tentacles around
the bell rim. The sense body of both these genera diffei'S in important particulars
from those of the families already described.

Fig. 85. — Dactylometra quluquecirra.

Fig. so. — Pelagia cijanella.

The aberrant families of the Discophora are among the most wonderful of this
group. A mention of a few of these may not be without interest. One of the most
abundant medusre at times in the neighborliood of the Florida Keys is a Discophore,
called by naturalists Linerges, and known to fishermen there as the " thimble-fish," " mut-
ton-fish thimble," and by similar designations. Under proper conditions the number of
individu.als of this strange genus is very great, and they may be often seen extending
in the water in long lines, where they are thrown by the tide-eddies and ocean currents.
The popular name of thimble-fish designates exactly the form which these medusm
assume. The bell is not unlike in size and shape a common thimble, differing consid-
erably in this respect from that of tlie other jellj-fishes of the Disco] ihorous type. The
bell has a brownish color on its lower floor, and its walls have a bluish tinge. Around
the bell margin there are si.xteen marginal lappets or rounded lobes, between which,
alternating with each other, there are eight rudimentary tentacles, and the same num-
ber of marginal sense bodies. Each sense body is covered by a gelatinous extension of

94

L 0 WER IN VER TERRA TES.

Fig. 87. — Linetyes mtrcuvlus, Ihiuible tish.

the bell walls of such a form that wlieii looked at above, it seems more like a cyst sur-
rouiiiling it than a hood serving as its cover. From the inner walls of the bell,
hanging into the bell cavity, there are placed sixteen dark-brown pigmented bags

which lie in a cii'cle with a radius about one-third
of that of the bell. Although the function of
these bodies is unknown, it may be predicted that
they will be found to serve as receptacles for
the elaborated food eaten by the medusa. Tlie
stomach of Linenjes is very simple in its structure
and never hangs outside of the cavity enclosed
liy the bell walls. "While the jelly-fish is in the
act of swimming, the marginal bell lappets are
commonly folded inward, forming a notched veil
which distantly resembles the so-called velum of
the liydroid medusa. At one time in the liis-
tory of the nomenclature of the jelly-fishes, the presence or absence of a veil was
used in designating the two great groups into which the meduste were divided. The
term Craspedota refers to those in which a well-marked velum is found, the Acraspeda
where the same is absent. Tlie Hjdroidea and Siphonoj)liora are craspedote, the Dis-
cophora are supposed to be destitute of a veil, and are therefore acraspedote.

Of the many aberrant families of the Discophora, none differ more widely
from the genera which we have already considered, than that of the Lijcernarid^,
or Galycozoa as they are sometimes called. In Lucernaria, the best known genus
of this family, we have a trumpet-shaped animal of comparatively small size, which
is attached by the smaller end, but has the enlarged extremity free. The free end
has a disk-shaped form, and in the centre there is an oj)ening into the body cavity
which is the stomach. Around the edge of the disk there are arranged at intervals
eight bundles of short tentacles or tentacular bodies of doubtful function. Tlie body
walls of one of our common species has a greenish color.

Several theories of the relationship between the Lucernaridie and the other
Discophora have been suggested, and their relations to this group are not recognized
by all naturalists. Of these theories there are two which seem to the
writer the nearest approximations to truth in regard to the affinities of
the family. Several naturalists, considering the attached mode of life
of Lucernaria, but 7nore especially its anatomy and what little is
known of its development, have supposed that Lucernaria is in
reality an adult in an arrested form or stage of development, and
that its nearest ally must be looked for in the young of other Disco-
phores. The young of many genera pass through a condition in the
progress of its development when it is attached to the ground, and
the allies of Lucernaria are by many naturalists recognized in these forms.

A second interpretation, suggested by E. Haeckel, has even more plausibility tlian
that already mentioned. It has this in its favor, that it refers the Lucernaria to the
adult and not to the young of another genus. A beautiful medusa was found by
A. Agassiz and by the Fish Commission in the Gulf Stream, and has been referred to a
genus long ago described under the name Periphylla. Periphylla is in fact a type
of a family called the Peeiphyllid^, and is in many respects one of the most aberrant
of the many genera which make up the Discophora.

Fig. 88. — iuccr-
7iaria auricultx.

JELLY-FISHES. 95

The resemblances between Luceriiarla and Periphylla are for the most part
anatomical in character, and so little is known of the development of both that there
is little j)ossibility of a comparison in this particular. The comjjarison, step by step,
of the many likenesses between the two genera would take us too far into special
studies of the peculiar anatomy of them both, but these points of likeness are of a most
important character, and show that, notwithstanding one form is attached and tlie
other free, they may be closely allied to each other.

The character of the development, and the different larval conditions which the
Disco])hora pass through in that growth, present some of the most interesting facts in
regard to these animals. In the progress of research into the anatomy and classifi-
cation of the lower forms of animals three curious zoophytes, placed in three genera,
had been described by different naturalists. These genera were called Scyphistoma or
Scyphostoma, Strobila, and Ephyra. It was suspected that they were not adults, but
in the early days of the history of marine zoology no one had any idea that these
animals had close relationships with one another. Tlie first and most important step
in a true understanding of the nature of the larvie of the medusie was made by Michael
Sars, by whom it was found that these three genera were one and the same, and
Steenstrup, shortly after, recognized that there exists in the medusis a true alterna-
tion of development such as the poet Ciiamisso had ]winted out is found in the forms
of the Ascidian genus tialpa., known as the " chain form," and the solitary or asexual
individual.

In late summer and autumn sjieciinens of Cyaiiea of large size are often taken in
which the membranous fold which hangs downward from the oral region of the disk
is loaded with white j^ackets or bundles. These bundles are composed of ova, and if
they are examined with a microscope of even low magnifying power will be found to
have already entered upon the first steps in their development. In other words the
genus Cyanea carries its young about and protects them in the folds of the mouth,
from the very youngest to some of the higher larval conditions. The highest con-
dition wliich it has in its career in the mouth-folds of the jiarent is what is known as a
planula. The planula is an elongated, spheroidal body whose walls are formed of two
or perhaps three layers, within which is a small cavity, and whose outer surface is
covered with vibratile cilia. The function of the vibratile cilia is that of progression
through the water, and, as a consequence, immediately on attaining this condition it
swims away from the fostering care of the parent, and shifts for itself in the water.
In this free-swimming or planula stage it remains until, freighted by the weight of
increased age, it can no longer swim through the water by the ciliary movements.
When that age comes in the progressive growth of the Cyanea, the embryo, which
was formerly spheroidal in shape with symmetrical poles, becomes jiear-shaped,
presenting an obtuse and a pointed j)ole which can easily be distinguished. The larva
next attaches itself by one of these poles to some fixed object, and the two following
stages in its growth are passed through in that condition.

Immediately after attachment there forms at the free end of the body a circle of
little protuberances which, as the growth goes on, become more and more elongated,
while in the centre of the circle, in the peri]jhery of which they lie, an opening is found
leading into a cavity in the interior of the body. The resemblance of the young
animal, in this first of the attached forms, to the common fresh-water /iyc/A/, which has
been described, is very striking. Tlie larva was one of those three supposed genera
mentioned above which were fonnerly thought to be widely different from any of the

96

LOWER INVERTEBRATES.

Fig. 89. — Scypliistoma of Aurtlia Jfavhlnla.

Discophoi-a. It was then called Scypliistoma or Scyphostoma, ami, notwithstanding
we now recognize that it is j^art of the life history of the young of another genus,

it is convenient to retain the name as char-
acteristic of the first of the attached larvae
of these animals.

The Scyiihistoma larva of Atirelia, for
the following larva has not been observed
in our Cyanea, although there is no doubt
that its development is identical witli tliat
of Aurelia, is followed by one called the
Strobila, which like the former is still
attached to some fixed object. In the
growth of the Scyphistoma, that part of the free end of the lar\a situated inside the
circle of tentacles, and in which the mouth lies, gradually rises liigher and higher,
forming an elongated cylinder of great relative size as compared with that of the
original body of the Scyphistoma, which lies at its base, and upon which it is borne.
There next forms on the outer wall of this cj'linder a number of parallel constrictions
which encircle the body of the cylinder in waving lines. These constrictions become
deeper as the larva gets older, imparting to it a remote likeness, as Professor Agassiz
has pointed out, to a " pile of saucers " resting below on the
remnant of the Scyphistoma body and increasing gradually
in size from the lowest member to the saucer which caps the
pile. The next change in the progress of the development of
Aitrelia, after the Strobila just mentioned, is one in which
the attached condition is abandoned and a free locomotor
larva again adopted. This condition, for a reason identical
with that mentioned with regard to the Scyphistoma, may
be called the Ephyra, and more closely ajiproaches that
assumed by tlie adult than any of the others. Tlio whole
fixed Strobila, however, does not break from its attacliment
and swim away as an Ephyra, but fragments of the same, or
individual saucers which compose the pile, in consecutive order one by one drop from
their attachment and swim away as perfect little Ejihyra'. The cycle is now complete,
and although the Ephyra differs greatly in form from the adult, yet still tliere are few
important additions, and no departure from a direct growth in passing from one into
the other.

By reviewing the history which has just been considered it will be seen that in
two of the intermediate larval conditions, known technically as the Scyphistoma and
Strobila, between the egg and the parent, we have a wide departure from the adult in
mode of life as well as external shape. "We have seen also that the Scyphistoma does
not pass directly as a whole into the Ephyra, but that it divides into fragments, each
of which becomes a perfect adult. From one Strobila a number of Ephyra3 are
produced without any conjugation of sexes in the attached animal. From this latter fact
the mode of reproduction is said to be asexual and the Strobila an asexual individual.
Gathering together the whole history of the develo]iment into one chain we find
it presents this remarkable circumstance. Between the egg and the female Discophore
from which it came there is an asexual, sessile larva which multijilies in an asexual
way by simple division, thus producing from one egg a numerous progeny, each of which

Fig. 00. -

Strobilia of Aurelia
Jfai'Ulula.

JELLY-FISHES. 97

has no known differences from the parents which j^rodnced the egg or spermatozoon.
The principle is a wide-spread one in the animal kingdom, and is known as the
alternation of generation. It is evident that the
Scyphistoma and Strobila, more especially the
latter, have a wide difference in shape from
the form of the adnlt Cyanea. They develop
directly from the egg and are asexual, while
the adults -which are developed from them are
sexual. Sexual animals produce ova which de-
velop into Strobila? as before. Here then is an
alternation of sexual with asexual forms of the
same animal, and the technical name of the
anomalous development is " Alternation of Gen-
erations," nowhere better illustrated than in the
Hydroidea and Discophora.

The develoiiment of the ovum of Ciianea into x, , „, r, , , , ,■.,■,,

the adult by a process of alternate generation, in

which intermediate larvje are fixed to some foreign body and reproduce the adult by
self-division, is not found in all the Discophora. As this method of growth may
be said to be indirect in character, another, called the direct from the absence of
these intermediate asexual conditions, also exists. In a direct development among
the discophorous medusas we have simply a continuous growth from the egg to the
adult. One egg produces only one adult. Such a development takes place in Pehujia
and one or two related senera.

Class III. — SIPIIONOPHORA.

Among the most beautiful of all the raedusaa is the group called the Siphonophora,
the tube-like jelly-fishes. These animals are all marine and free swimming, and
although they often have a hydroid-like shape, which resemblance becomes more marked
when we study their anatomy, they are never attached to tlie ground as are the mem-
bers of the Hydroidea. They are found in all oceans, although the tropics seem to be
richest in the variety of these animals, and those from the Mediterranean have up to
the ])resent time been the most carefully studied and described.

As their name signifies, the Siphonojihora are characterized by a tube-like body,
which is generally so nuich elongated that it takes the form of a small axis or stem.
Although thei-e are. several genera in the group where the body does not assume a
tubular form (of which one of the most common is Physalia), a tubular liody seems
as a rule characteristic of the group.

The relationships of the Si]5honophora to other meduste have been variously inter-
preted by different authors. By the majority they are regarded as comparable to the
Hydi-oidea, and are often called the free-swimming hydroids, in distinction from those
already considered which are fixed. Others still compare them with the gonojihores
of the hydroids, some of which as the genus Lvixia bud off from the side of their
manulirium new individuals, which later develop into medusoe like their parent. The
Siphonophora would be regarded by them as similar to the parent with many attached
young. While many facts can be mentioned in supjiort of either of these theories, it
may be said that the differences which exist between a free medusa and an attached

VOL. I. — 7

98

LOWER INVERTEBRATES.

hydroid are not very great, and although at lirst sight it might seem as if the two
theories involve very different comparisons, they are in reality identical.

Order I. — PHYSOPHOR^.

One of the most interesting forms of Siphonophora is the
genus Agalrna, the name of which dates back to the days of
Eschscholtz, the father of the study of actinology. It is the
type of a family known as the Agalmid^, and lielongs to a
larger group of Pliysojihoraj or float-bearing Sijihonojihora.
The genus Agalma when floating in the water, will be found
to be made up of two kinds of bodies. The flrst of these are
transparent, crystalline in appearance, and are easily detached
from their connections with each other ; the second are more
opaque, flexible, and sm.iller, while they are moi-e tenacious in
their attachments to the animal. All are strung together on a
common axis or stem which is very flexible in its character.

The Agalma as it floats in the water is of a very fragile
nature. So delicate is it in fact that it cannot be raised out of
the water in the hand without the appendages being torn from
their connections with each other. The only way to capture it
entire is to j^lace under it, as it moves about in the water, some
receptacle which will hold liquid, allowing it to float in
with the water. The water contained in the receptacle
and the animal can then be raised together out of the
sea. Even when the greatest care is shown in its
capture it retains its appendages but a short time
when kept in confinement, and soon loses them
all and shrinks to an insignificant size as
compared with its former proportions.
The axis or stem of the Agalma
is a most characteristic structure.
It extends from one extremity
of the animal to the other,
and affords an attachment
to all the appendages
which make up the
whole. It is very
flexible, colored a
rosy pink, is hollow
throughout, and about
the diameter of a knit-
ting-needle. At one
end, which may be
called the upper ex-
tremity of the axis,
the stem is enlarged into a small globular body which is called the air-bladder or
float. This float contains a little sac filled with gas, and in some related genera

Fig. 92. — Agalma elegans ; a, float; b, nectocalioes:

covering scales: tf. feeding

polyps; e, tentacles and tentacular knobs; /, tasters; g^ sexual bells.

JELL Y-FISHES. 99

has for a function the suj^port of the axis in the water. In Agalma, however, it
is so small that its functional importance in this respect is very sliglit. The axis
of the Agalma is divided into two regions, one of which lies adjacent to the float,
and is called the nectostem, and the other, more distant from the same, the polyji-
stem. In larger specimens the length of the nectostem is about one-third that of
the polypstem. The former bears a number of appendages of interesting char-
acter called the nectocalices. Tliese bodies are situated in two rows or series, and
are glassy clear in their transparency. Their union with the stem is of a very fragile
nature, and easily ruptured when the animal is raised out of the water. If we exandne
a single nectocalyx we shall find that it resembles closely a medusa bell (hydroid
gonophore) in which the walls ha^e a more or less polygonal shape. This form is the
result of a flattening of two opjwsite sides of the nectocalyx in order that it ma\- tit
closely in the series of which it is a member. Each nectocalyx has a cavity within,
which opens into the surrounding water through a circular orifice, partly closed by a
thin, washer-shaped body called the ^-eil. The apex of the nectocalyx is situated
opjiosite the external ojjeuing, and marks the point of union of the bell and the necto-
stem. On either side of the apex, embracing the nectostem, the bell walls are con-
tinued into gelatinous horns which closely interlock Avith similar jirojectidiis from
nectocalices situated in the opposite series.

The arrangement of the nectocalices on the nectostem is as follows : There are two
rows or series of these bodies placed diametrically opposite each other on the axis.
Each series is composed of a number of nectocalices placed one above the other, fitting
closely together by the flat faces on the outside of these bodies. The gelatinous horns
already mentioned interlock with corresponding bodies from the opjjosite series. By
the close approximation of adjacent bells on their flat faces, and the interlocking of
bells from opposite series, a certain rigidity is given to this jiortion of the animal,
notwithstanding the delicate attachment to the stem.

The disposition of the nectocalices causes all the bell openings in each series to
point in the same direction, or almost at right angles to the length of the axis. The
action of the nectocalices is as follows : They are, as their name implies, structures
for a propulsion of the Agalma from jilace to place through the water. When water
is taken into their bell cavities, by a violent contraction of the bell walls it is violently
forced out through the opening into that cavity against the surrounding water in
which the medusa is floating. The necessary result of this action is that the animal
is forced through the water in an opposite direction from that in which the resistance
takes place. By a nice adjustment of the different bells, acting in concert or indejiend-
ently, almost any motion in any direction can be imjjarted to the Agalma. Just
below the float on the nectostem there is a small cluster of minute buds in which can
be found nectocalices of all sizes and in all conditions of growth.

The attachment of the nectocalyx or swimming bell to the nectostem, not only
serves to move the animal from place to place, but also renders it jjossible for the
swimming bell to receive its nourishment. Although the nectocalyx resembles very
closely a medusa, it is a medusa bell without a mouth or stomach. It is not capable
of capt\iring nourishment for itself, but is dependant upon others for that iJurjiose.
Tlie nectocalyx has a system of tubes on its inner bell \valls which communicate with
the cavity of the nectostem by means of a small vessel which lies in the peduncle by
which it is attached. Through this system of tubes the nutritive fluid is sui)plied to
the nectocalyx from a common receptacle, the cavity of the stem. In the largest

100 LOWER INVEllTEDRATES.

specimens of Agcdma which I have studied, tliere were seventeen jJairs of well-devel-
oped nectoealices.

The aj)pendages to the polypsteiu are somewhat different in character from those
of the nectostem, and are of several kinds, differing in character, size, and shape. The
first and most prominent of these are known as the covering scales. They are trans-
parent, gelatinous bodies, and are found throughout the whole length of the polyp-
stem. Their shape is quadrangular or almost triangular, and they are united to the
axis by one angle. The upper and lower faces are flat, and the whole apjiendage has
a thin, leaf-like appearance. Through its walls from the point of attachment to the
distal angle there runs a straiglit unbranched tube which communicates freely with
the cavity of the stem. The covering scales are easily detached, and are incapable of
voluntary motion. Their function seems .to be to shield the structures which lie be-
neath them.

Below the covering scales three kinds of bodies hang from the ])olypstem. They
are known as the jjolyintes or feeding stomachs, tasters, and sexual bells. The polyp-
ites are the most conspicuous of these bodies. They have a flask-like shape, and are
united to the polyjistena by one extremity, while the free end has a terminal ojiening
which is a mouth. The walls of the cavity of the jiolyjiite are crossed longitudinally
by rows of cells which have been compared to a li^er. In the cavities of the polypites
the half-digested food can be seen through the walls. The nutritive fluids formed
in these bodies are poured into the cavity of the axis, there to be distributed
throughout the different ai)])endages of the animal. When indigestible substances, as
the hard parts of Crustacea, are taken into the stomach they are thrown off again
through the mouth-o]>cning. I ha^e never- seen the polyjiites more than seventeen
in number, and they hang at regular intervals along the whole length of the i>olyp-
stem.

One of the most prominent bodies next to the nectoealices and covering-scales in
the Agalma are the so-called tentacles, which hang from the base of the polyjiites,
and which when extended are very long. The tentacles of A(jahna are long, highly-
flexible, tubular filaments whose function is the capture of food. At times widely
extended their length is little less than that of the Affalma axis itself. At other times
they are drawn up under the covering-scales at the base of the polypite, and have a
very diminutive size. Along their whole length they are dotted with crimson pendants
of minute size which are called the tentacular knolis. These will be found, on close
study, to be of a very complicated structure. Their true function is somewhat prob-
lematical, but they are supposed to assist in the ca]iture of the food. In addition to
the well-developed tentacular knobs which dot the whole length of the tentacles,
thei-e arc many half-gi-own bodies of the same character clinging to the base of the
polypite.

Alternating with the poly]>ites at intervals along the polyjjstem are found very
curious bodies called tasters, which have a close likeness to the flask-shaped feeding
zooids. These bodies are without a mouth-opening at their free extremity, -(vhile from
their base hangs a long, highly-contractile filament which is destitute of tentacular
knobs. The tasters have an internal cavity which is in free connnunication with that
of the axis of the animal. Vai-ious functions have been assigned to the tasters, but
none without objections seems yet to have been hit uj)on. Their usual position is in
clusters midw.ay between the adjacent polypites. The term taster is somewhat mis-
leading, for these bodies do not have gustatory functions.

JELLY-FISHES. jqI

The sexual bells are of two kimls, male ami female, and both are found iu grape-
like clusters, the male near the base of the tasters and the female near the polyjiites.
If we isolate one of the members of a cluster, we find that it has a bell-like shape, and
that Uie ova or spermatozoa are found on a proboscis within. Each boll hangs from
the cluster by a tender peduncle which arises at its apex, and each female bell contains
a single ovum.

The growth of the young Agahna from the egg to the adult is of a rather comiili-
cated nature. When cast in the water the egg is a tiny, transi)areut sphere barely
visible to the naked eye. After fecundation, and obscure changes similar to a seo--
mentation of the yolk, a slight protuberance arises at one pole. This prominence is
formed of two layers between which, in a short time, a third layer is also formed.
The outer layer is the ectoderm, the middle the mesoderm, and the internal the endo-
derm. Between the endoderm and the remainder of the egg there is a cavitj- called
the primitive cavity. As the embryo grows older the elevation at one pole increases
in size, and the proportion in thickness of the middle layer, as compared with the
ectoderm and endoderm, becomes very large, while the ectoderm becomes very
thin. The prominence has now assumed a helmet-like shape, and fits like a cap
over the remnant of the yolk. The whole larva in this stage of growth is called the
primitive larva or LizziOr-stVige, and the cap-shaped covering, the primitive scale.
The i)rimitive scale is an embryonic organ which is lost in subsecpicnt develo|)ment
of the larva.

Innnediately after the primitive larva stage there is found to <levelo[i under the
primitive scale an air-bladder or float, which first appears as a little bud near the open-
ing into the primitive cavity, which has now taken the form of a tube in the primitive
scale lined with endoderm. At about the same time also there appears a coverino--
scale of very different form from either the caji-like primitive scale or the coverino--
scale of the adult Affcd/na, which have already been described. The float is the
permanent float of the adult, while the second formed covering-scale, like that of the
first, is also embryonic and larval in character. The larva has now the followino-
parts: 1, The remnant of the yolk; 2, a cap-shaped covering-scale; 3, a second em-
brj-onic covering-scale, and 4, a float. As the larva grows older more covering-
scales like the second appear, and the beginnings of a tentacle and tentacular knobs
are seen at the adjacent end of the growing larva. At the same time the yolk
becomes elongated, and in its walls appear reticulated masses of red or crimson
pigment.

The tentacle first formed as well as its pendants, the embryonic tentacular knobs,
are transient in character. They differ essentially from the adult knobs, and are
confined to this stage in the development of the larva. Meanwhile the primitive scale
is lost, and a circle of covering-scales of the second kind appears at the base of the
float. This larva is called the Athorybia larva from its remote resemblance to a related
adult genus called Athorybia. The appendages of this larva are : 1, a float ; 2, a crown
of embryonic covering-scales; 3, the remainder of the yolk-sac with an attached
tentacle and temporary pendants.

The next following larval condition of Agahna is one in which the embryonic
covering-scales have disappeared and new scales like those of the adult have formed.
Four well-developed nectocalices appear on a nectostem, and an adult jiolypite bearing
the characteristic pendants of the adult has grown on the extremity of the short polyp-
stem. A remnant of the yolk-sac, however, still persists, and from it depends an embry-

102

LOWER INVERTEBRATES.

^4)

onic tentacle and its characteristic side branches. The Physopliora hirva resembles

the adult in all ])articiilars, except size, and the ])resence of the last of temporary
organs later to disap])ear in the growth of
the Agahnu, viz., the embryonic tentacle.

Several other genera of Physophores are
so closely allied to Agalma that they are
j)lacecl in the same family. One of the most
interesting of these is the genus Agahnoj^sis,
which differs from Agalma in its slighter
form and the intimate structure of its ten-
tacular knobs. JIalistemma has also a pecu-
liar tentacular pendant which differs from
tiiose of AgaliiiM or Agalmojwis. In the
adult knob of Agalma the following struc-
tures are found : 1, an involucrum ; 2, a sac-
culus ; 3, terminal filaments and vesicle. The
involucrum is a membranous sac which covers
the knob wlien the other jsarts are retracted. ^ v^j
The great mass of the knob is made up by
the saccuhis, which is corkscrew-sha])ed and
dark crimson in color. At one extremity it
is fastened to the inner walls of the involu-
crum, tlie free end bearing two terminal fila-
ments and a vesicle. The various genera of
Agalmidse differ in the eliaracter of this knob. /'/

Agalmo2isis lias a saccuhis and involucrum, Init no vesicle, and

only one terminal filament. I/alisteiiana, probably the type of

another family, lias no iiivolucruni, while it possesses a spirally-
coiled sacculus and a single terminal filament. The genus

CrystuUodes has tentacular knol)s like those of Agalma, and is

by some authors made a species of this genus. It differs, how-
ever, from Agalma in the rigid nature of the axis, in the shape

of the covering-scales, and in minor points in the anatomy of

the nectocalices.

The genus Stephanomia, a name which has been a])j)lied to //

genera of Siphonophora of widely different form, was given by ; 'W^^'K "L

the elder Milne-Edwards to a Physojihore in which there are

many series of nectocalices ajipended to the ncctostem. S. con-

iorta is one of the most beautiful and graceful of all the Siphono-

])hores as liy the combined movement of its many swimming-bells

it gaily swims along in the water. It is peculiar in this respect,

that the polypites are mounted on a long peduncle, which also

boars the covering-scales .and the tentacles. The tentacular knobs

resemble more closely those of JIalistemma tlian of Agalma. It

may be regarded as the type of the family Forskaliad.e.

ne ot the most heautitul genera ot 1 iiysopiiortd.e is the

interesting animal known as P/igsophoni, called in the dialect of the Messina fishermen,

" Boguetti." Pliysophora is remarkable in j^ossessiiig no poly]istein, but in ])lace of this

Fig. 93. — 'I'lMitacular
knob of At/atmopsis.

\\

A

fl

7/

^\

JELLY-FISHES.

103

structure the axis is enlarged into a bag-like inflation. There is, however, a well-
developed nectosteni and two series of nectocalices as in Agalma. Around the cir-
cumference of the inflation, which takes the place of the polypsteni, the tasters with
their short, tentacular filaments are arranged side by side. The jiolyjiites and sexual

Fia. 95. — rhijsophora hudrostatica.

bodies are found below these structures. No true covering-scales exist in the genus
Physojyhora.

One of the largest of all the Physojihoi-as is the genus Apolemia, the type of
the Apolemiad^, which is called by the Italian fishermen by the suggestive name of
"lana di mare." In this beautiful Siphonophore we have, as in other float-bearing
medusaj thus far considered, a double row or series of nectocalices, but unlike the
last mentioned genera, there arises from the nectostem, small bodies resembling

104

L 0 WER IN VER TEBRA TES.

rainute tasters which wave about in the water with great freedom. The polyp-
stem also, instead of being covered throughout its whole lengtli with covering-

>..'€^

Fig. 96. — Portion o£ Apoltmla.

scales, has these structures arranged at intervals and in clusters, each with tasters,
polypites, and sexual bodies.

Oedee II. — PNEUMATOPHOR.E.

There are two genera of Siphonophora closely related to each other and to the
group of PhysophoriB already studied, which are now looked ujJon as forming a group
by themselves. These genera include the well-known Portuguese Man-of-War or
J^/iysalia, often erroneously called by sailors the Xautilus, and a less common genus,
Mhizophysa, one of the most bizarre forms of these animals.

Physalia is one of the most common of all the Siphonophora in tropical oceans.
The most conspicuous part of this animal, as it floats along on the surface of the water,
is an enlarged air-bladder, six or eight inches in length. On the upper side of this
float there is a raised crest colored by brilliant blues, yellows, and pinks. On the
under side of the same there hang a great variety of appendages of several kinds.
There are feeding-mouths -or polypites, flask-shaped bodies resembling tasters with
long tentacles, which, as the animal floats in the water, extend far liehind it in the
water as magnificent streamers, and grape-like clusters of sexual bodies. The Phi/salia
is wholly destitute of a tube-like axis, and as it floats on the surface of the water,
resembles more a bladder -with richly variegated walls, than the tube-like forms which
we have already considered.

The closest relative to Phi/salia, as far as anatomy goes, to which aflinity also what
is known of their development adds additional evidence, is the strange genus Mhizo-
physa. Mhizophysa is a simple skeleton of a siphonophore. It is the axis of an

JELLY-FISHES.

105

Fig. 97. —Physalia aretlmsa. Por-

Agalma stripped of all its apijendages, excejit feeding i^olyps and sexual bodies. There
is in it no distinction between nectostem and polypstem, and no means of voluntary

motion. The float is particularly large
and has an apical opening tlirougli
which its contents communicate with
the surrounding water. The feeding
polyps hang from the stem at regular
intervals when extended, and midway
between them appear on the same axis
botryoidal clusters which are called the
sexual organs. Tentacles hang from
the bases of the jaolypites as in other
related siphonophores. The tentacular
knobs have, however, a highly charac-
teristic form which varies with different
species in number and general anatomy.

Order III. — DIPHY.E.

In all the genera thus far studied,
there is always a float at one extremity
of an axis when such was present. In
no case is a float missing, although often-
times it is functionally unimportant.
In none of the remaining Siphonophora,
on the other hand, is a float present.
These last meduste may conveniently
be divided into the Diphya;, in which
tuguese nian-ot-wai-, one-flfth there are one or two nectocalices, and

natural size.

the Hippopodise, floatless forms in •which
there are several or more than two swimming-bells.

One of the best marked families of the Diphy;iE is the Dipiiy-
ID-E, of wliieh Diphyes is a tyj)ical genus. This genus and most of
its I'elatives is smaller than the majority of those already studied,
and are easily distinguished from the former by the absence of a
float, and the presence of but two nectocalices. The two swim-
ming-bells which are possessed by Diphyes are of somewhat differ-
ent form. The anterior is conical in shape in order to facilitate
rapid progression through the water, while the posterior which
lies behind it, seems to perform the greater jiart of the work in
the progression of the medusa. As in Af/alma, onward motion
is caused by the resistance of the water as it leaves the bells on the sun-ounding
medium in which the animal swims. The motions of the nectocalices are spasmodic
and not long continued as in the Ayalma and other Physophorse. The axis of
DljjJi.yes hanging from the interval between the two bells, is a long, filamentous,
flexible structure not unlike that of Agalma. It is highly contractile, and has a cavity
throughout its entire length. The polypites arise at intervals along the length of the
stem, and are in no respect peculiar. Each polyjiite bears a tentacle and tentacular

Fig. !

106

L O WER IN VER TEBRA TES.

knobs, or pendant side-branches. At tlie point of attachment of tlie polypite to the
axis, we also find a transparent bell-shaped covering-scale and a cluster of sexual bells

with eggs and spermatozoa.

Each cluster of bodies near

a j)olypite ultimately sepa-
rates from its attachment to

the Dlphyes axis, lives in-

dejiendontly, and is called

a diphyizooid.

There are several families

related to the Dipliyidre

which might be mentioned.

They differ from it in the

character, size, and general

anatomy of the two neeto-

caliccs. One of the most

marked of these is Pruija^

a solitary genus composing a

family called the Prayii)J3.

In Praya there are two

nectocalices wliicli are of

al:)out equal size, and have a

rounded or semi-ovate form.

The l)ell walls are not as

rigid as those of Piphi/es,

and their motion less spas-
modic. The axis is very

long and flexible, and the

polyjjites, found at intervals

along its length, are pro-
tected by a helmet-shaped

covering - scale, beneath

which are found clusters of

sexual bells moimted on

short p e d u n c 1 e s. The

genus is one of the most

striking of tlic many beau-
tiful genera which . charac-
terize the Siphonophore

fauna of the Mediterranean

Sea. I have also observed

a fragment of a large Praya
near Fort Jefferson, Tortugas, Florida.

The fourth of the large groups into which the true Siphonophora may be divided
is called the HippopodIjE from a genus sometimes called Hippopodms^ which has a
highly characteristic and jieculiar structure. Gleba { nippopocUus) is in most respects
related to the Diphyw, but unlike them has more than two nectocalices. There is no
float and no extended axis with individuals found at intervals in its length. No polyp-

FlG. 99. — Diphycs.

JELLY-FISHES.

107

stem is developeil, and the neetostem has little in common witli that of Aycdma. The
iiectocalices are of characteristic sliape and different from those of any other siphono-
j>]iore. Each bell has the shape of a horse's hoof,
and has a very shallow cavity and rigid walls. As
far as yet known -the Hi2)poi)odi£e have no dijahyi-
zooids such as exist in several genera of the Dij)hya\

Order IV. — DISCOIUEJE.

Among the many interesting forms of Medusae
related to, and by most naturalists included in the
Siphonophora, are two beautiful genera called Vclella
and Povpita. These, with a genus liataria, which is probaljly the A'oun<>- of one or
the other, make up a group called the Discoidea.'.

Velella has borne the name which designates its most striking peculiarity since the
middle of the fifteenth century, on account, ])erhaps, of a somewhat fanciful likeness
to a little sail. It is commonly called in Florida, where it is sometimes very abundant,
the " float," and is likewise commonly confounded with the Phi/salia or Portuguese
man-of-war. The body or disk of Veltlla has an oblong shape, flattened upon its

Fig. 101.

-Dipbyizooid of Praya.

ViG.WI.—TeUlla limbosa.

upper and lower sides. The float is coni]iosed of a number of concentric compart-
ments in free communication with each otlier, seven of which o])en externally in a line
extending diametrically across the disk. In the whole diameter there are fourteen
such openings, seven in each radius.

A triangular sail rises on the upper side of the l^clella disk and extends diagonally
across its surface. It is firmly joined to the u]i]ier ])late of the float. Over the trian-
gular sail as well as the float, there is stretched a thin, blue-colored membi-ane, which is
continued into a variegated soft rim along its border and around the rim of the float.
In our most common American Velella, which often reaches a length of four or five
inches, the portion of the rim of this membrane around the di.sk is entire; in some
species, however, it is continued into elongated ap])endages.

The most im]iortant appendages are found on the under side of the Yelella disk

108 LOWER lyVERTEBRATES.

whicli is commonly submerged as the animal floats on the surface of the water. Of
these pcrhaijs the most prominent is a centrally placed body which hangs downward
below the remaining appendages, and is open at its unattached extremity. This
structure is the feeding-mouth or polypite, and is single in both J'elella and J'orjnta.
In the zone just surrounding the polypite we find a large number of small appendages,
each of which has a thread-like shape bearing along its sides a number of little trans-
parent buds in all conditions of growth. Each of these little bodies ultimately sepa-
rates from its attachment, and in the form of a minute jelly-tish, not larger than a ptin-
head, swims about endowed with independent powers of life for a considerable length
of time. The medusa which has thus separated is known as a Chrysoniitra. Surround-
ing the bodies last mentioned on the lower surface of VeleHa, there is a circle of
feelers of bluish color which- are conuuonly in constant motion. One of the most
prominent superficial differences between Porpita and ydella is the total absence of
a triangular sail in the former genus. They are commonly found associated together,
and often accompanied by a. third jelly-fish allied to both, called Rataria.

Class IV. — CTENOPHOEA.

The highest of the jelly-fishes, both on embryological and anatomical grounds, are
known as the Ctenophora. In these animals that characteristic of higher forms of life
known as bilateral symmetry appears for the first time. An obscure symmetry which
has been called by some naturalists bilateral, appears among the Siphonophora, and
even in the Hydroidea. In the Ctenophora, however, it is more plainly indicated than
in either of these groups.

One of the earliest mentions which we have of the ctenophorous meduste we owe
to Martens. Freiderich Martens was a ship's physician or a ship's barber, as he stjdes
himself, who accompanied Captain Scoresby in a voyage of exploration into the Polar
Seas. He first found one of these beautiful medusas in the neighborhood of the island
of Spitzbergen. Eschscholtz was the first to recognize the common likenesses between
the different members of the group, and gave to them the name of Ctenophora or
comb-bearing meduste.

The Ctenophora take their name, as he first pointed out, from the existence on the
external body walls of eight rows of viViratile ])lates called combs. These combs are
arranged in such a way that in flapping they strike u]wn the ^\-ater, and by their mo- '
tion the jelly-fish is driven along thi'ough the water. We find here for the first time
since our studies of the Ca?lenterata began, a large group of animals where movement
in the water is produced both by special locomotive organs and contractions of the
body.

The varieties in form in the bodies of different Ctenophora is very great. In some
genera they appear as long ribbon or belt-like creatures which move through the water
with serpentine movements, in others as transparent caps or globular gelatinous masses
over which the rows of combs shine with most lovelj' iridescent colors. No greater
variety of more beautiful genera is to be found anywhere among the medusse.

Cestus, called also the Yenus Girdle, is perhaps the most striking genus of the
Ctenophora. Its shape departs the most widely of all the Ctenophora from that of the
medusoid types. In Cestus the body of the jelly-fish has a girdle or belt-like form, and
is moved more by the contractions of the body than by the rows of combs which fringe
its edges. The .animal is very transparent and extremely tender, so that it is with the

JELLY-FISHES. 109

greatest difficulty taken from tlie water witliout breaking. Its motion tlirongli the
water is a graceful undulation to which l)ody contractions and vibrations of the condjs
contribute.

The mouth of Cesti/s is situated midway in its length between the two extremities
of the belt-like body. On either side of it there hangs a single short tentacle which
protrudes from a tentacular sac. Opposite the mouth there is a sense-body, or otocyst
as it is commonly called, in which is situated a compound otolith. The rows of combs
upon the external surface of the body of Cetttus are not as conspicuous as in some
other genera, but the course of their lines can be easily traced. The enormous exjian-
sion of the two lateral lobes of the l)ody which give a girdle-like form, imjiart to the
rows of combs which lie in these regions an extraordinary development as compared with

I'll;, ill.;. — r, sills riihris, \ eiins girdli.'.

those which lie in the intermediate regions or on the flattened sides of the body. The
adult Cestus reaches a length of from two to three feet, and is one of the largest as
well as most beautiful ctenophores of the Mediterranean. There is scarcely any color
in its body walls.

Of the many genera of medusae closely or remotely allied to Cestus, one of the
most interesting and least known is a genus called Oci/roe from the Gulf of Mexico
and the Caribbean Sea. This genus, like many other ctenophores, and especially like
Cestus, is very transj^arent, and has on the external body-surfacei, eight rows of vibra-
tile combs, the lines of which converge at a point near that pole of the animal in \\hich
a sense-organ is situated. One of the most extraordinary things about Oryroe is the
great development of two opposite sides of the body into wings. In Cestus the oppo-
site sides of the body are so developed that .a band or belt-like form is given to the

110

LOWER INVER TEBRA TES.

animal, but in Oci/roe these lateral developinents take on the form of wings or similar
bodies. Cestus moves througli the water by a slight luidulation of the body, while
Ocyroe does the same by a flapping movement of its greatly developed lateral lobes,
and by their beating iijion the surrounding water. When Ocyroe is at rest, the lateral
wings are widely extended, giving to the animal a remote likeness to Cestus. When,
however, motion is attempted, the lobes are raised above the horizontally extended
position which they occupy at rest, and then violently swung downward, passing
through almost 180°. This flapping of tlie two wings in concert is continued several
times, and in that way the animal is proiielled through the water. The function of
the rows of combs in the movements of the medusa is secondary to the flapping move-
ments of the lateral winofs.

The body of Ocyroe, from two sides of which the wings arise, is of oblong, oval
shape, with a mouth at one pole, and a cluster of otoliths in an otocyst at the opposite.
There is no vestige of tentacular appendages near the mouth, and the lips are undi-

Ocijrot crijstalltna.

vided, smooth, and highly flexible. Ocyroe thus far has been taken only from the
waters of tropical America.

In colder latitudes as on our New England coast, we have a beautiful ctenophore
called Bolina, and another very closely allied genus known as Mueniiopsis. These
medusae are in many respects most closely allied to Ocyroe, or rather Ocyroe seems an
aberrant form of these more northern jelly-fishes. Although the same lateral lobes
exist in both genera, their importance in Solinn, as far as movement is concerned, is
much less than in Ocyroe. They are also seldom or never carried extended horizon^
tally at right angles to the body, as in the curious genus Ocyroe. Bolinct, is one of the
most transparent of the comb-bearing meduste. The body is very gelatinous and
highly phosphorescent. The sides of the body are developed into two larger lappets or
lobes which are carried or hang vertically instead of horizontally. On account of the
contractile powers of the body walls, Bolina can vary its outlines very considerably ; as
a rule, however, when the body is seen from the side, it has an oval or elongated form.
Eight rows of vibratile combs contribute to the propulsion of the medusa through the
water. These lie upon the external surface of the body, and arising from the pole
opposite the mouth-opening, extend to the more distal edge of the lateral expansions
to the vicinity of the mouth. From the great development of the lateral lobes, the
four lines of vibratile combs which cross these bodies are much longer than those
which lie on the body regions between them. Two tentacles are found hanging from
the sides of the body of Bolina. These tentacles are of diminutive size in the adult,
and are remnants of structures which in caily conditions of growth were very much
more developed.

Pleurobrachia and Bougainvillea.

JELLY-FISHES.

Ill

Four other curious appendages called auricles are found on the sides of the body
in the grooves which lie on opposite ends of a horizontal diameter of the body, and
which are enclosed by the edges of the lateral lobes. These auricles are simply exten-
sions of the body walls on the sides of the mouth, and their edges are skirted by vibra-
tile plates somewhat like those found on the exterior of the body in the lines mentioned
above.

The stomach and chyme tubes, vessels analogous to veins and arteries, in JBoUna
do not differ greatly from the same structures in other Ctenojihora, but are highly
characteristic as compared with sunilar bodies in other medusaj. The mouth of liolina
is a narrow, elongated slit, opening with a correspondingly flattened receptacle called
a stomach. From the end of this stomach opposite the mouth, there arises a number
of vessels which jjass to various regions of tlie body. One of tlie most important ol
these is continued directly to the aboral pole of the medusa, and is known as the fun-
nel. Of the others, four, after a bifurcation, jiass to the vicinit}' of the rows of combs,
and following a meridional course, eventually join each other in pairs near the ojjpo-
site pole of the jelly-fish from the sense-body or in the lateral lobes. There are two
tubes which originate from the base of the funnel and extend along the sides of the
body to the tentacles which from their characteristic course have always attracted
attention. Their function seems to be to convey the nourishing fluid to the tentacles
into which they eventually open.

There are several genera of ctenophorous medusfe allied to JBolina. One of the
most pompous of these, as well as the largest of the comb-bearing jelly-fishes, with
enlarged lateral lappets is a genus called Chiaja. This genus is remarkable in manj
particulars, but more especially in the great length of the auricles which appear as
long, filament-like tentacles, and the very complicated course
of their chymiferous tubes.

Many classifications have been made of tlie Ctenophora, but
as yet all are open to objections of some kind. One of the last
suggestions with this subject in view emphasizes the presence or
absence of the tentacles. By this classification we Avould have
the Ctenophora divided into the Tentaculata and the Nuda,
accordingly as tentacles exist or are wanting. In the genera
which we have already considered, with the exception of Ocyroe,
well-developed tentacles are found either in the larval or adult
condition.

Probably the best example, however, which might be men-
tioned of a tentaculated ctenophore is the genus C'l/dippe or
Pleurobrachia. There are often in our New England bays and
harbors, after a southeasterly wind, a number — myriads at times
— of little transparent gyrating spheres, not larger than a com-
mon marl)le. These little gelatinous spheres move through the
water with a great variety of motion, and seldom change in any
important particulars the regular spherical form of their bodies
in the manner characteristic of the genera of Ctenophora to
which we have referred. When the cause of this variety in
motion is sought out, it will be found that on the surface of the body there are a num-
ber of iridescent lines extending from one pole to another, and that each of these lines
is formed of a number of minute comb-like bodies such as exist in other Ctenophora.

Fig. 105. — Pleurobrachia
rlwflodactyla ,■ only a
portion of the ten-
tacles shown.

112 LOWER INVERTEBRATES.

It is by the strokes of these bodies on the surroimdiug water that the jelly-fish is
moved about from place to place.

Tlie tentacles of Pleurohrachia, oftentimes almost wholly inconspicuous they are so
securely packed in little lateral pockets on either hemisphere of the medusa, are most
important structures in the economics of this beautiful medusa. It often happens,
when the jelly-fish is at rest, that the tentacles are extended from their pockets,
stretching far outside of this receptacle. Their length when extended in this way is
so great that it seems impossible that they can be retracted into the tentacular pockets.
The tentacles are two in number, each tentacle bearing a large number of side branches
of brownish color, and in the movements of the medusa are often thrown into the most
fantastic shapes.

The Ctenophora Nuda, or those cteno])hores which are destitute of tentacles, are
represented by a very beautiful medusa called Stroe. This is perhaps one of the most
remarkable jelly-fish which we have yet considered, although it is without doubt one
of the lowest in its organization. The form of the body of this animal is that of a cap
or rounded sac of very sim]ile structure.

If we closely consider the structure of this animal it will be noticed that, extending
longitudinally across the outside surface of the body, there are eight rows of combs as
in the other Ctenoijhora. At the pole of the body tliere is a sense-body in a similar
position to that of the sense-body of other genera. The whole interior of the body
serves as a stomach, and into it there ojiens a moutli of very great size. The stomach
will often be found gorged with food, and the animal swollen to double its natural
size by the mass of food collected in this organ. This animal is indeed one of the most
ravenous genera of medusie. There are no tentacles in the genus Beroe and no sign
of tentacular sacs. The chymiferons tubes have a very simple course in the walls of
the body, extending from common origin to the vicinity of the mouth in an almost
direct course with, however, many side branches. The color of our common JBcro'e is
a delicate pink.

Class II. — ACTINOZOA.

Much discussion, hai:)pily now for the most part of the past, hangs about our knowl-
edge of the nature of the Actiuozoa or corals. Their relationship to animals was first
recognized by Peysonelle, who records his observations in the quaint language of a
former century. The word Actinozoa, of comparatively modern date, has an almost
exact equivalent in the older term Zoojihyte, and refers to a great variety of animals
fixed to the ground like plants, and possessing in common with them certain superficial
resemblances. They all have remote likenesses to a plant or flower, with which for a
long time in the history of science they were confounded. It includes the great families
of reef-building corals, and has an added interest on account of the many questions which
suggest themselves in relation to the method of formation of coral reefs and coral islands.
In the general structure of their bodies the Actinozoa differ somewhat from the Hj'drozoa,
but the difference is not of such great imjiortance as to call for a wide separation in a
scheme of classification of the two. The differences would appear at first sight very
great. Nothing for instance could seem more different than the soft, gelatinous body of
the medusa and the stony mass of a coral, and yet this difference has no homological
meaning, and as far as general structure is concerned the two are identical. In the
medusa; the body is so filmy and transparent that it is often wholly invisible as the

CORALS.

113

animal swims in the water, and the sense of touch is necessary to siipj^lement that of
sight in order to know where the animal is. In stony corals on the other liand we find
secreted in the animal tissues a very hard, cal-
careous substance which forms a skeleton, and,
when the secretions of a number of individuals
are united, an axis or head upon which the corals
build or secrete their skeletons. When we view
a white brancli of coral we see nothing of the
animal save its dried and bleached skeleton,
from which most of tlie organic nature has dis-
appeared. If we could go to the tropics and
study the medusiE and corals alive many points
of likeness might be traced in their general
structure.

We are accustomed to associate with al]
animals a certain amount of motion from place
to place in the medium in which they live. In
the Actinozoa, however, we find very few of the
adults endowed with locomotive powers, and
all, as a general thing, are fixed to some foreign
body. The solid carbonate of lime which the
majority of the corals secrete in their tissues is,
in respect to its method of formation, identical
with all secretions in animal bodies. It is not
the work of the coral any more than the shell
of the clam or tlie covering of the lobster is the
work of the animals which they enclose and
])rotect. It is an internal or external formation
by secretion, and as a consequence coral animals
are not mechanical builders any more tlian any
other animal can be called the mechanical con-
structor of its shell or skeleton. Many of the
Actinozoa have no power of secreting hard
matter in the form of a skeleton, and the bodies
of such have a soft, gelatinous character, while
in their tissues, as in those of the medusre, a large proportion of Avater is found. The
solid secretions of coral animals, commonly known as coral, is sometimes erroneously
supposed to harden on exposure to the air. This opinion is probably well founded as
far as coral rock, a chemical product of tlie cementation of coral sand in a way to be
explained, is concerned, but is wrong as regards the coral in the form secreted by the
animal. Altliough it aji]>ears to harden by the loss of animal mattei', the skeleton
itself changes but very slightly, if at all, in its hardness after the death of the animal
from which it came.

The genus Actinia, a soft-bodied Actinozoan wliich has not the power of secreting
carbonate of lime, is for various j'easons the one commonly taken to illustrate the
anatomy and characteristics of the group. Actinia, found in almost all seas in the
temperate as well as torrid zones, is represented by a large number of species, the ma-
jority of which are of comparatively large size. The Sea-Anemone, MetricUum
vol.. I. — 8

Fig. 106. — Monoxenia, young lialcyouoid polyp.

114 LOWER INVERTEBRATES.

marginatum, our New EngLand vVctinia, has been chosen to illustrate certain of the
important general features in the anatomy of the grou]).

Metrklium is common almost everywhere on the New England coast in sheltered
pools left by the tides, on spiles of bridges, and on rocks near low-water mark. Under
the name of sea-anemone it is known to collectors of marine curiosities as the common
zoophyte from Eastport to New York. In no place have I seen the species larger than
on the spiles of Beverly Bridge and at Nahant, but equally giant specimens have
pi'obably been taken from other localities. The diameter of the largest MetricUum
found in the former locality measured, when expanded with water in its tissues, a little
over ten inches in diameter. Forms of Actinaria allied to Metrklium from the Florida
Kejs and Bermuda attain a gigantic size, often fifteen to eighteen inches in diameter.
When the Actinia is seen from one side it will be found to have a cylindrical body
firmly fixed at one end to some foreign object, and bearing at its free end a circle of
tentacles surrounding a central mouth. The tentacles are thickly set together, are
very movable, and when the animal is alarmed are quickly drawn to the bod)\ The
whole body and the tentacles are very much inflated with water, which at the will of
the animal can be expelled from the body through the mouth, the body walls, and the
tips of the tentacles, where there are small orifices. When inflated with water the
body and its appendages are all expanded, but when this water is expelled the animal
shrinks to a shapeless lump, the tentacles are drawn back, and there is little resem-
blance to its former condition.

The internal structure of Metridium is of a character typical for most of the Acti-
nozoa. If we make a horizontal section through the body about one-half the distance
between its attached and free extremities the cross-section thus made will present
the following characters. In the centre lies a cavity, the stomach, whose wall is
held in position by radiating partitions passing from it to the outer walls of the
body. Inteiinediate between these partitions there are radiating walls or se]ita which
arise from the outer body walls but do not extend to those of the stomach. The body
walls from which these partitions all arise are, as a general thing, thicker than those
forming the partitions, and in their sides there are openings through which the water
at times leaves the body cavity.

The method by which the 3Ietridium feeds is very simple. The food captured by
the tentacles when the anemone is expanded is passed from one member to another
through the mouth into the stomach. Here digestion takes place, and after the soft
portions have been digested the harder parts, skeletons, shells, and the like, are thrown
off again through the mouth by which they entered the stomach. The fluid passes
from the stomach through an ojiening opposite the mouth into the body cavity, bath-
ing the interior of all the organs which lie in that place.

Special organs of respiration are not unknown among genera of Actinaria allied to
Metridium, but in this genus probably the whole external and internal surfaces of the
body contribute their part in the performance of this function. In Metridiinn special
organs of sensation are of a very low grade of organization and of the simplest kind,
as would naturally be expected from the attached life of the animal.

Reproduction among the Actinozoa presents some of the most interesting features
connected with these animals, and in the case of the coral colonies in which the reef-
builders live, is the most important factor in the determination of the ultimate form.

Three kinds of reproduction, which are known as generation by fission, by gem-
mation, and by the laying of eggs, or ovarian, occur in the Actinozoa. The first two

A GROUP OF EUKOPEAN SEA-ANEMONES.

1. Tlielia craasi^omlg, tWck-petalled sea-rose. 2. Safiarfitt parasitica. ,•!. Actinnloha (liantkus, sea-pink.

4. Sagartm viduata, "the widow." 6. Sagarlia rosea, red anemone. 6. Bunoiks mmmacea, warty anemone.
7. Anthea cerms, green anemone.

CORALS.

115

methods are asexual in their character, the last sexual. In reproduction by a fission
we find a sunple voluntary self-division of a single individual into two or more second-
ary animals. In many reef-building corals this method of increase is most natural in
order to increase the size and style of growth of a colony of these animals. Among
the solitary forms like Metridium it is seldom found. A second mode of increase,
a reproduction by gemmation or budding, is much more common than that of fission
and is found in the solitary as well as the communal forms of Actinozoa. In the
formation of a bud we have a very simple method of reproduction. In such a case
there simply appears on one side of the base of the body, or, as in some genera,
on the disk surrounding the mouth, a small protuberance, which is a simple elevation
of the body walls. From this simple beginning of a bud we pass to a more developed
condition in which the protuberance has become a small coral animal attached to tlie

Fig. 107. — Crambactis arabica-t sea auemone.

parent at one extremity which is its base, and with a free exti-emity furnished witli a
mouth surrounded by a circle of tentacles in most respects identical with those of the
motlier. The bud from the parent has every resemblance to the parent, and can live
independently although still attached, and drawing nourishment in jiart from her
through the base of attachment.

All the Actinozoa reproduce by means of eggs. The ova pass through the condition
of a ciliated planula which is free-swimming and sometimes parasitic in its youth.
Phenomena similar to those of alternation of generations have been found in some
genera, but as a rule the development is direct from the egg to the adult. Special
features in the development of individu.al genera will be touched upon as we continue
our account of these animals.

The Actinozoa are commonly divided into two great groups, easily distinguished
from each other, and known as the Actinoida or Zoantharia, and Halcyonoida or Alcy-
onaria, which includes, roughly speaking, the reef-builders in the first instance and

116

LOWER INVERTEBRATES.

the " sea-fans," " sea-pens," and their allies in the second. Anatomically, the two
groups are distinguished, in part, as follows : In the Actinoid corals we find a large
number of internal radial septa and numerous external tentacula about the mouth.
When the nimiber of these organs is small they are generally in multiples of six, and
in most instances there are no lateral ai)pendages to the tentacles. When hard matter
is secreted in the tissues it is commonly in the form of carbonate of lime. The second
great group of Actinozoa, called the Halcyonoida, differs from the former in the
possession of eight, or a multiple of eight, tentacles and body septa, while the former
almost universally bear side branches and appendages. In those genera where a
skeleton exists it is tough and elastic, oftentimes of very great hardness, as in the
genus Isis and the well-known ornamental coral of commerce.

Oedek L — ZOANTHARIA.

The so-called Actinaria, which are referred to the Actinoid corals, include a large
number of interesting genera. As a general thing, these genera are solitary in their
mode of life, and often reach a great size. One of tlie best known genera of the
Actinaria is the genus Metridhnn, of which we have already spoken.

Many of the Actinaria are either
free-swimming in their adult form, are
parasitic, or live with their bodies par-
tially hidden in the sand ; still others
are attached to the ground. They do
not, as a rule, secrete a calcareous or
horny skeleton, and their bodies are
usually very soft, without even the
needle-like spicules which occur in
the soft forms of the Halcyonoida.

One of the most interesting of the
Actinaria is the genus Edwardsia,
which is not attached to the ground,
but lives in the sand in its adult form,
■while in younger conditions it is free-
swimming, even after the tentacles
have reached a considerable size. The
young JEdwardsia was at first mis-
taken for the adult condition of an
Actinoid coral, and was described
under the name of Araehnactis.
Later, however, it was shown to be
simply the free-moving young of the
"■enus Edu-anhia. PeaeJda, another
<i-enus of Actinaria, is parasitic in the
mouth-folds of the discophorous jelly-
fish, Cyanea.

The Zoantharia, which are reef-
building corals, are closely related to the Actinaria, and although generally found
in colonies, are sometimes solitary in their habits of life. One of the most nearly

Fig. lOS. — Fiinfjia symmetrica, three times the natural size.

CORALS. 117

related to the Actinaria of all the Actinoids ■which secrete lime is a beautiful
genus, which bears the highly suggestive name of Fungia. It is the largest of
the solitary lime-secreting corals, and often reaches a diameter of from six to
eight inches. It is disk-shaped, with a large number of radiating partitions, or
septa, which extend from the centre of the disk to a periphery not bounded by a
vertical wall. The tentacles are not placed in a circle around the periphery of
the disk, but are found irregularly disposed over its whole up2>er surface. Fungia,
in its adult condition, is not attached to the ground, but lies in the coral lagoons in
ratiier sheltered places. In the younger stages, however, of its development it is a
fixed form, and passes, according to Semper, through a larval condition comparable
to the strobila of the Discophora, exhiliiting a true alternation of generation. Rejiro-
duction also takes place in Fimgia by fission and gemmation. The larger species
of the genus are found in the Pacific and Indian oceans. A small species, Fungia
symmetrica, was dredged by Pourtales, and afterwards by Mr. Agassiz in the " Blake,"
in the depths of the Straits of Florida and the Caribbean Sea.

There are several very fragile comijound corals which in their young conditions
resemble Fungia, and which on that account naturally come in the neighborhood of
this genus. One of these, called Mycediuni, is one of the most common corals in
the sheltered lagoons of the Bermudas and along the Florida reefs. Mycedium
fragile, called in the Bermudas the Shield Coral, has a thin, fragile disk, easily broken,
which hangs to the submarine cliffs a little below low-water mark. This disk has
a chocolate-brown color, which bleaches, as do most coral skeletons, into a beautiful
white. Upon the upper side of the disk we find two kinds of coral animals. One
of these is centrally placed, and is the mother of the colony, or the parent from
which the others have formed by a budding. The remaining individuals are smaller
than the central, around which they are arranged in concentric circles, which increase
in number with the diameter of the disk upon which they are formed. It will, there-
fore, be seen that we have in Mycedium two kinds of individuals, a single, large
central animal, which is the oldest in the colony, and many smaller, which it may
at once be said are formed by budding from the original. Nothing is yet known
of a reproduction in Mycedium by self-division or by the deposition of ova, although
there is every reason to suspect that both of these methods of formation of new
colonies really exist.

One of the most common genera of Actinoid corals is called Madrepora. Although
rarely, if ever, found as far north as the Bermuda group of islands, it is one of the
most common of the reef-builders, and especially near the western termination of the
Florida Kej-s it forms great banks miles in extent, whose upper surface rises to within
a few inches of the low-water level.

One of the most abundant species of Madrepore is M. cervicornis, a branching
sjiecies, which sometimes attains a large size. The difficulty of comprehending the
structure of Madrepora comes from the fact that in each branch of one of the dendritic
sjiecies, as cervicornis^ we have a large number of different individuals arising from a
common axis. If we take a termin.al fragment of such a branch, we can see that its
very tip is formed by a small rounded body of calcareous nature, in the interior
of which there are radiating partitions passing from centre to circumference, as in the
genus Fungia. The peripheral ends of all these septa are bounded by a calcareous
wall connecting them all, which is absent in the last-named genus. If we study care-
fully the slight excrescences upon the sides of the branch, we find that although

118

L 0 WER INVER TERRA TES.

smaller there they have iu all important respects a similar structure to the terminal
individual.

The branch of Madrepore, when alive, presents an
altogether different appearance from that which the
bleached skeleton has. By carefully studying the soft
portions of a growing coral of this genus, it will be
noticed that the terminal and lateral individuals have
the general appearance, as far as their soft tissues are
concerned, of a minute sea-anemone or a typical Acti-
nozoan. Each individual has a brownish, cylindrical
body, composed for the most jiart of watei-, with a
central stomach, into which 02)ens a mouth at the free
end of the animal.

In the species which we are now considering, the
less conspicuous bodies, which arise from all sides of
the calcareous branch upon which they are formed,
originate as buds from the base of the terminal indi-
vidual. In order to understand the relationsliijjs
between the large terminal and the smaller lateral
individuals, both of which form a colony in the branch
of a Madrepore, we must regard the former as a j)arent
form from which all the lateral have budded, and of
which they are the young. Suppose that we go back
in the development of the branch to a time when there
was but one individual where now we find a branch
W'ith the colony clinging to its sides. At that time
there would be formed a small, single individual, bear-
ing every likeness to that which is now terminally situated on the branch. As growth
goes on from that early condition, buds arise one after another from its base and sides
in a manner identical with that which we find in
the genus 3fetridmm, which w'e have already
described. As the coral with its attached bud
at the base grows, there is deposited near its
attachment a larger amount of lime than is nec-
essary, so that in fact the processes of life are
impeded by the surplus of solid matter in the
tissues. The result is that the lower part of
the animal becomes dead matter, while at the
same time the soft portion of the same is grow-
ing upward, and is rising above the solid matter,
now too much solidified to allow vital processes
to go on in that portion of the Madrepore. The
original animal, however, still lives, and its place
is not wholly taken by the buds which earlier
in its history formed upon it. A surplus of solid deposition in the walls of the base
of the bud cements it firmly to the parent, while from the live part of the original
polj-p, now slightly elevated above the plane in which it formerly was, there forms a
second bud, a third, a fourth, and so on. A repetition of the formation of too much

Fig. 109. — Mmfrepora verrucosa.

7 rn -c^

Fig. 110. -

- Section uf Miuhrpusa verrucosa,
eularged.

CORALS.

119

lime for vital functions takes place continually, and with equal pace the live portion of
the original individual mounts higher and higher until a branch, similar to that with
which we started, is eventually formed. It can thus be seen that there is in the
branch of coral a larger individual, which is the original polyp with which the
colony starts its growth, and smaller individuals, or lateral buds, which have from time
to time, as the first polyp grows, budded out on its base and sides. When, as often
happens, a lateral branch is protruded from the sides of another branch, we simply
have a bud which partakes of the character of the larger individuals rather than its
neighboring lateral buds. It grows by the same laws as the branch from which it
originates, and as in the first, so in this, small lateral buds which resemble those on the
parent branch are freely formed upon it.

A second species of 3Tadrepora, although departing widely in general form from
the first, is closely allied to it in generic characters. This sj^ecies is known as ^^ja^
mata, and instead of a branching habit, occurs in flat, massive slabs, on the upper

Figs. Ill and n2. — Heliastrma hdiopora, braiu-coral, witli aud without llesUy pails.

surface of which the different individuals are irregularly distributed. Blocks of such
fragments generally grow at greater depths than 31. ceroicornis, and when water-
worn form the so-called coral boulders which make the foundations upon which the
reef rests. They play no small part, by their soliditj-, in the successful resistance of
these islands to the encroachments of the sea.

Some of the most massive genera of Actinoid corals are those known as the
"brain-corals," or "brain-stones." There are several genera which are commonly
confounded in this nomenclature, and all such have many similar anatomical peculiari-
ties. The genus Diploria assumes a hemispherical shape, varying in size from a few
inches to several feet in diameter. Its external surface is covered
with serpentine furrows, which recall vividly the convolutions of
the brain, and probably suggested the name of brain-stones for
these corals. Over the curved surface of a live brain-stone is
stretched the soft organic parts of the coral, while in the super-
ficial furrows lie the stomachs, which have a similar serpentine
form to the convolutions in whicli they lie. Upon the surface
of the brain-stone, arranged in lines, are found rows of mouths,
each opening into that stomach or jiart of the stomach which lies
just beneath them.

Another genus allied to Meandrina and Diploria is known as 3Ianicina. This
genus is not commonly as large as either of the former, and does not have the brain-
like shape. Its upper surface, however, has the same furrows as the genera above

Fig. 113. — Three
luouths of Heli-
astrcEOf enlarged.

120

L 0 WER IN VER TEBRA TES.

Fig. 114. — Astrma pallida.

mentioned, in which Hes the stomach. 3Ianicina is commonly found on the floor of
a coral lagoon, but is not attached to the bottom. Here also belongs the genus
Heliastrwa.

Several other genera of Actinoida assume, in the manner of their growth, the shape

of hemispherical heads, although
they do not have a convoluted
surface like the true brain corals. ^
One of the best examples of these
is Astraa, a coral in which the
colony has a globular form, but
without superficial canals. The
different coral individuals in
Astrcea are placed side by side
over the M'hole surface without
being arranged in lines, while
every individual is externally
almost wholly distinct from
every other in the colony. The
mode by which animals of this genus reproduce their kind, and increase the size of
the community is by simple self-division or fission. When the single individuals, by
their growth, exceed a certain size, they spontaneously divide into two similar wcUt
formed smaller individuals.

The only Actinoid coral which secretes a stony base found in New England waters
is a beautiful little genus known as Astrangia,
which occurs in small patches in the crannies
and clefts in the cliffs along the southern shore
of New England. At Newport, R. I., on the
most southern point of the island, there are sev-
eral localities where beautiful colonies of these
animals are found. This is, however, but one
of many localities which might be mentioned.
The calcareous base which the Astranyia se-
cretes is inconsiderable in size, and forms only
a slight crust on the surface of the rocks.
It builds no considerable reefs or coral de-
posits of any size. The animal itself is one
of the most delicate and beautiful of all the reef-building corals.

No living genus of corals better illustrates the formation of new individuals by self-
division than that known as Mussa. Here we generally have a limited number of
individuals, never branching, but attached to each other at their bases. Almost every
fragment of one of these corals shows individuals with evidence of a self-division,
either just beginning, partially formed, or wholly comjileted. In the parent individual
before any sign of division begins, the upper extremity or distal end is of circular form
and the coral itself has an irregular trumpet-like form, fastened by the smaller end to
some foreign object. The first sign of change in the original Mussa prejiaratory to a
fission, is the elongation of the disk-like shape or a lengthening of its axis, by which
the two opposite sides closely approach each other. This growth nltimately leads to
a condition in which the two opposite sides approach, and the disk of the coral is

Fig. 115. — Astrangia danm.

CORALS.

121

divided into two individuals, both of which have a common stomach and a common
basal attachment. The complete fission or division of the original individual into two
is accomplished in the last stage, which is one in which we Jiave the same common
base of attachment, bearing at its top two perfect individuals, which have resulted from
the self-division of the single animal with which we started.

Order II. — HALCYONOIDA.

The second large group of Actinozoa is called the Alcyonoida or Halcyonoida from
the genus JSalcyonium, supposed to be the nest of the " Halcyon " or king-iisher
of the Greek fables. To this division belong the " sea-fans " and " sea-whips,"
so-called, and many others, some of which are widely aberrant in general char-
acters. So different in structure from the typical " sea-fans," are many of the genera
now thrown among the Halcyonoids, that they ai-e probably destined later, when a
more perfect classification is made known, to be the nuclei of new groups of equal
rank.

The colonies of Halcyonoids have commonly a branching form, are flattened in fan-
like shapes or extended into long, flexible whips. In TubijMra, or the organ-pipe coral,
we have the hard parts tubular in shape. The amount of deposition of solid matter in
their tissues varies considerably. In certain genera all hard inorganic depositions are
wanting, and the body is soft and without skeleton. In still others, secretions in the
form of spicules are well developed.
Of those which have a hard skele-
ton, we find all degrees of hard-
ness, from a simple horn-like axis
of the " sea-whips," to the extreme
hardness of the ornamental coral
of commerce.

In the classification of the Hal-
cyonoids many systems have been
attempted, but the subject is still
in an imsatisfactory condition, and
at present there is little uniformity
among naturalists in regard to the
limits of families and genera. A
well-marked genus called Anti'p-
athes is separated from the Hal-
cyonoids by almost universal con-
sent, as the family Antipatharia, and seems to stand between the Actinoids and the
group which we are now considering. The likeness of Antipat/ies to the sea-fans is
best seen in the branching character of its axis, while the number of tentacles and tlie
absence of side branches to these organs, ally it more closely to the majority of the
Actinoids. One of the most interesting species of AntijxUhes is the well-known A.
columnaris. In this species we have a very interesting case of a worm building a
tube from the smaller lateral branches of the coral or by its presence causing a modi-
fication in the mode of growth of the coral. Upon one side of the axis of the Anti-
pathes, the worm, a true annelid, places itself, and the small lateral branches of the
axis in the immediate neio-hborhood are modified into a columnar network forming the

Fig. lie. — Section o£ red-coral.

122

LOWER INVERTEBRATES.

walls of a tube in which the worm lives surrounded by the case, bearing the relation-
ship of a true messmate to the coral upon which it is found.

Of the true Halcyonoida the genus Salcyonium of the Halcyonid^ is one of the
most interesting, which is sometimes designated by the suggestive name of dead-men's-
fingers, looking not very unlike a human hand with the fingers i-emaiuing as mere stumps.
Although in general appearance Halcyonium resembles the soft corals, well-marked
spicules of beautiful shapes are found regularly arranged in its walls.

The common sea-fan, Rhipidogorgia flabellum, which we select as illustrating the
GoEGONiD^, is one of the most common Halcyonoids of our tropical and semi-tropical
seas. The fan-like shape which the colony has is the result of the fission of many
lateral branches, large and small, forming a network often of great fineness. The sea^
fan has a hard central axis, and a still softer rind which can be easily broken off, and
at the death of the animal is almost wholly deciduous. In this softer rind are found

the spicules, and from it the animals directly arise.
There is a great variety in the forms of the differ-
ent genera of sea-fans, and the colors are sometimes
very striking; in many, bright reds and yellows
predominate with purj)les and browns.

The sea-whii>s, of which there exist a great vari-
ety of forms, assume either the shape of low, branch-
ing, shrub-like zoophytes, or long, unbranehed,
straight or spiral rods. Their colors are sometimes
black, often light brown, and occasionally, as in a
Chrysogorgia from deep watei-, golden.

One of the best known of all the Ilalcyonoids
is the genus Coralliuin so much prized as the orna-
mental coral of commerce. The greater quantity
of this coral which is used is gathered in the Medi-
terranean where the most extensive fisheries are
situated on the western coasts of Italy, the shores
of Sicily and Sardinia. The city of Najiles,
where the cutting of the coral into ornaments is
a great industry, is a great centre of coral com-
merce, and many pounds of the more precious
varieties are yearly sold there. The commercial
value of different coral fragments dejiends upon
the size, but more especially on the tinge of color
which they have. The ] link rose-color is esteemed
the most valuable, while "ruby" varieties are
ranked among inferior wares. Much, of course,
also depends in individual sjiecimens upon free-
dom from blemish, and ])urity of color. The
coral has from the earliest times been cut into
cameos by lapidaries, and its use in ornamenta-
tion reaches far back into classical times. The
word has been derived from the Greek, Koqr],
daughter, a highly fanciful comj)arison of these most beautiful gems to the daughters
of the sea goddesses.

Fig 117 —

Fig. 118. — Keii cor;iI polyps, enlarged.

Cordlliiiiii ntliruin. red coral.

CORALS.

123

A genus called Jsis is closely allied in many respects to CoralUum, and approaches
it very intimately in the great hardness of the axis. While portions of this axis are as
hard as that of CoralUum, the stem is not continuous, but is formed of hard and soft
articulations, alternating with each other. The hard joints are securely bound together
by softer and more flexible articulations, permitting a slight bending of the axis. The
IsiD^, including Isis, Mojjsea, and one or two allied genera, are often used for orna-
mentation, but no considerable traffic with them has taken place. Isis flexibilis, which
extends from the latitudes of the Caribbean Islands to the coast of Norway, is
one of the most graceful of this family. It is sometimes found in deep water, often in
the profound depths of the ocean.

There are many genera allied to Isis, some of which are found in deep seas, which
present most interesting connecting features between the Isidaj and the true sea-fans
and sea whips. One of the most interesting of these is a beautiful ochre-colored coral
called Melitcea. The branches of llelitcea, like those of Isis, arc composed of alter-
nate stony and soft joints, of which the size of the latter are relatively much larger
than the former, which appear as bead-like expansions. JI. ochracea is reddish yel-
low in color, and has the branching habit of the majority of the true sea^-fans. It is
found in the Pacific and Indian oceans, many specimens bearing Singapore as the
locality from which they were taken. It is of considerable size, and seems to connect
structurally the family of
Isidaj with the true sea-
fans. •

Of the many aberrant
genera of Halcyonoida,
the genus Tuhipora or
the organ-jiipe coral, the
type of the family Tubi-
POEIDJE, departs the widest
in general appearance from
that of the majority of Hal-
cyonoids. In this genus
we find no radiating par-
titions of hard secretion as
in most corals, but instead,
a number of tubes arranged
side by side separated from
each other by a slight space
and bound together by hor-
izontal floors. In these
tubes live the tubipore coral, and to them it owes its suggestive name. The color is a
deep red, and the coral community often reaches a considerable size. It is, however,
very fragile, and easily crumbles under the action of the waves, presenting a great
contrast to the harder species of CoralUum, Isis, and Jlopsea.

The sea-pens, Pexxatuhd^, embrace a few most interesting forms of Halcyonoida.
In Pennatula riihrum, the likeness to a quill-pen is very close. In this coral a central
axis extends from one end to the other of the body, inside a sheath from one-tliii-d of tlie
length of which there hangs, on either side, ojiposite each other, rows of leaf-like disks
supported by calcareous spicules. Upon the faces and edges, more especially in the

Fig. IW. — Titbijjora, organ-pipe coral, natural size.

124

LOWER INVERTEBRATES.

latter position in many allied genera, 2)olyps are borne as in all corals. It commonly
happens that many of these polyps are aborted in character, those upon the stem

especially assuming this form, so that there
is present a ])oIymorphism of most simple
character.

In lienilla, an extraordinary genus allied
to Fennatula, we have a still greater differ-
ence between the two kinds of zooids found
on its body, and a still better illustration of
the princiijle of ])olymorpliism so well seen
in many of the jelly-fishes. The form of the
genus Benilla departs widely from that of
almost all other Actiuozoa. The bodj^ has
a thin, flat, kidney shape, from which liangs
a short, highly flexiiilc hollow stem. There
is no hard axis such as is found in some
other Halcyonoids, and the body walls are
flexil)le throughout. The poh'ps are borne
upon one surface of the disk-like body, and one of
these, known as a Hauptzooid, has a prominent size
and specialized character. Menilla, like Pennatidu, is
a free coral, and its attachment to the sand is of the
loosest nature as compared with the stony base of
Corallium and Isis.

The family of Ujibel-
LULiD^ is also of widely
aberrant and most inter-
esting character. The
several genera which
compose it are most
closely allied to the Pen-
natulidse, and are as a gen-
eral thing found in deep
seas. The genus Umbel-
lularia \vas descrilied long
ago, and the accurate figure given of it remained, for many
years, the best and only account of the animal. Although
discovered in comparatively shallow water, the great exjilor-
ing expeditions of the jjast twenty years have again brought
the animal to light, this time from profound depths.

In Utnbellularia we liave a long axis, more or less firmly
attached by one extremity, while from the other there
arises a cluster of polyps in the form of a terminal tuft.
These polyps are of two kinds. Some ajijiroach closely
the regular form of the Halcyonoids, while others resemble
the abortive zooids of Pennatula and Sarcodictyon. "We
have here another expression of a law of polymorjihism already jiointed out in lienUla,
and already developed at length in our account of the Siphonophora or tubular medusie.

Fig. 120. — UmbeJhilaria gr(enlandica,
natural size.

Fig. 121. — />/«'o;rfes, se.i-peii, one-
fourth natur<al size; a, a single
individual, a little enlarged.

CORALS. 125

CORAL ISLANDS.

The study of tlie formation of coral islands is one of the most fascinating connected
with the Actinozoa. So long as naturalists limited their attention to the coral life of
the Mediterranean and other European seas, where no great coral reefs exist, this part
of the subject attracted but little attention, but with the awakening of interest in all
branches of natural science at the beginning of the present century, more especially
at the time of the great exjiloring expeditions sent out to the troi)!cs by the different
governments, the human mind naturally turned to these islands, and the mode of their
formation became a subject of scientific interest. The subject has a geological as well
as a zoological side, and touches on several questions of physical geograjihy. It is,
moreover, almost incomprehensible without a clear idea of the chemical nature of the
solid lime secretions of the coral body, which plays the most important part in the
origin and growth of tliese characteristic islands.

"While the present subject is considered in relation to the coral animals, it must
not be supposed that they alone make the coral reefs. Although most conspicuous in
this woik, there are others of very great importance in their formation from the time
the foundations are laid on the sea iloor up to that wlien the reef emerges from the
waves in the form of an island. Of these might be mentioned a few genera of stony
hydroids as Millepora., molluscan shells of all kinds, Bryozoa, Radiolaria, pelagic
Protozoa, and genera of marine Alga'. Many instances of coral islands formed in part
by any of the last mentioned, will no doubt suggest themselves. A few examples will
suffice for illustratioji. Cooper's Island, one of the large coral islands of the Bermuda
group, has a sandy beach which is almost wholly made up of oceanic Foraminifera.
The beach adjacent to the landing at Fort Jefferson, on the Tortugas, Florida, is wholly
formed of fragments of a large Nulliporc, an Alga which secretes lime in its tissues,
and is found alive in large clum]3s in the moat about the fort. Shelly Bay at the
Bermudas is composed almost entirelj' of fragments of lamellibranchiate shells ground
into a fine sand. Strata of rock formation in the Bermuda of four or five inches in
thickness are made up entirely of the shells of land Helices, some of great size, firmly
cemented together. While these and many other animals contribute to the formation
of the coral islands, corals seem essential to their growth, for we find characteristic coral
reefs confined to the zone which by the thermal conditions of the water limits the
home of these animals.

The distribution of reef-b>iilding corals follows a number of most interesting haws.
In latitude their home is limited north and south of the equator by the water isotherm
of 68° Fahr. These lines projected on our globes follow no parallels of latitude, often
being widely separated from the equator and then approaching to its immediate
vicinity. While the reef-building corals are limited to this zone it must not be
supposed that all genera of Actinozoa are hemmed into these narrow limits. Many
corals, some of which secrete a calcareous skeleton, are found in all latitudes as far as
naturalists have explored the marine life.

Tlie distribution at present of coralline life on the globe is very different from what
it has been in the past. While reef-building cor.als now never venture into latitudes
higher than 35°, the evidence drawn from fossil coral banks shows that in older times
they were found in very high latitudes. In the North Atlantic Ocean at the jiresent
time the northern limit of extensive banks of coral is the lonely Bermuda group in the
latitude of 32° N.

126 LOWER INVERTEBRATES.

The distribution of the coral islands in longitude presents some very interesting
facts. As a general thing it may be said that the eastern shores of the continents are
richer in coral banks and islands than the western. The eastern coast of North
America, for instance, has the Florida reefs, the great Bahama bank, one of the largest
in the world, the reefs of Yucatan, Honduras, and Cuba. On the western sliore of
North and Central America there are no extensive coral reefs. The eastern border
of Australia has a wealth of coral life, while the western is almost a desert as far as
plantations of these zoophytes are concerned. The Atlantic coast of Africa has no
extensive reefs, while that washed by the Indian Ocean is fringed by very extensive
banks. If in studying this distribution in longitude we consider also the limitations
in latitude we find the following law to hold good. While in the longitude of the
eastern shores of the continents the reefs extend far from the equator, in that of
the western border they are, when found, limited to the immediate vicinity of the
equator. An explanation of this curious fact in coral distribution is found in the
direction of the great equatorial currents of the Atlantic and Pacific Oceans. Tliese
currents cross the ocean from east to west, and as they approach the eastern continental
borders they divide, one branch flowing to the north the other to the south along the
coast lines. Two streams of warm water are thus continually carrying the oceanic
isotherm of 68°, which limits the home of the reef-builders, into higher latitudes, and
broadening the zone in which these sensitive animals can live. On the western coasts,
however, we find an opposite condition of things. The equatorial current is there
fed by branches fiowing in opposite directions, in which the water is colder since they
are setting from higher latitudes towards the equator. The result upon the coral
organisms is that they are hemmed into narrow limits on this side of the ocean by the
diminution in the breadth of the zone which tliey can inhabit.

The distribution of corals and the limitation of coral islands by such local phenom-
ena as rainfall, volcanic activity, and the like, present many very curious facts. The
almost constant changes in the level of the sea floor ]>roduced by volcanoes would
necessarily destroy plantations of growing corals in the immediate neighborhood. It
commonly happens that coral and volcanic islands are found in intimate association,
while it is probably true that all oceanic coral islands rest on volcanic bases. Where
the volcanic forces are active, the lava poured into the ocean, or the ashes raining
from tlje air at times of great eruptions, generally destroy tlie coral banks. A good
illustration of this fact may be seen in the Sandwich Islands, where the most southern
members of a chain of islands which make up the group are volcanic and destitute of
extensive coral banks, while the northern are almost wholly formed of coral. The
almost uninterrupted volcanic activity in the southern members of this group has
prevented the formation near them of coral banks, while at the north, where active
volcanic forces are now unknown, the islands are almost wholly coralline. The eastern
members of the Lesser Antilles, as Barbadoes, are coralline, while the western are
volcanic. In the island of Guadeloupe we find the same law of local distribution to
hold in a single island, the eastern extremity being coralline and the western volcanic.
This distribution of corals in the Antilles jirobably dejiends upon tlie direction of the
ocean currents in the neighborhood, or perhaps upon the constant direction of the winds
by which the ashes from the volcanoes are blown to the leeward, thus killing the growing
corals on the western side. It may perhajis be tliat the jirofound dejtths to whicli the
Caribbean Sea sinks to the westward of the lesser Antilles prevents the corals obtain-
ing a foothold on that side, while the shallows on the eastern shores are better suited

CORALS. 127

for the luxuriant growth of these animals. The situation of mountains on or near the
coast of the continents or elevated islands, and the direction in which the rivers of
such flow to the ocean, also has its influences on the distribution of coral islands in the
iuiinediate vicinity. One of the very best illustrations of this limitation of coralline
life is seen in the island of New Caledonia. Most of the rivers in this large island,
according to Dana, empty themselves into the ocean along the western coasts, while
the eastern side is almost wholly destitute of streams of fresh water. Along the
eastern border we find an almost continuous coral reef, and no signs of coral growth
on the western. Fresh water is destructive to coral life, and rivers bring from the
land large quantities of silt, which is also detrimental to its growth. To these causes
may perhaps be traced the almost total absence of coral formations on the northern
border of South America, near those parts of the coast line where the Amazon and
Oronoco pour their great volumes of fresh water into the Atlantic.

There are several very curious facts, many of which are not yet explained, in
regard to the geographical distribution of genera of corals. The coral fauna, for
instance, of the Bahamas and Florida regions is widely different from that known to
exist on the western coasts of Central America. The corals of the latter region have a
closer likeness to those of the Indian Ocean, almost its antipodes as far as geographical
position goes, than they do to those of the Caribbean Sea, separated from them by
only the narrow isthmus of Darien. Madrepora cervicornis, a most abundant coral
along the Florida Keys, is very rare in the Bermudas.

Corals are found at almost all depths in the ocean. Tlie greatest profusion of
life lies in the zone between the surface and the depth of one hundred to one hundred
and fifty feet. Deep sea corals, of an interesting character from their relationships
with extinct genera, are found at great depths, even in the abysses of the ocean.

The general distribution of coralline life in the different oceans is as follows : —

The Atlantic Ocean has several very considerable coral reefs and coral islands, all
of which are confined to its western border. In the South Atlantic a large and peculiar
reef is found extending many miles along the southeast coast of Brazil. In the
chain of islands called the Lesser Antilles we find that the frequency of coral reefs
increases as we go towards the northern members. Along the northern shores of San
Domingo, Hayti, and Cuba, Ave find extensive reefs. There are evidences also of
elevated coral banks in these islands. The peninsulas of Yucatan and Honduras
are fringed with coral shoals, and large banks exist on their northeastern and northern
borders. The line of Florida coral reefs, extending from Loggerhead Key, the
extreme western island of the Tortugas, to the southern extremity of the peninsula of
Florida, is one of the most instructive collections of coral islands in the Atlantic
region. The Bahama Islands are composed wholly of coral, and are the largest con-
tinuous bank of grow'ing coral in the North Atlantic Ocean. Its extension is as great
in length as the whole eastern coast line of the United States from Maine to Florida.
The only example of an oceanic coral island in the North Atlantic is the Bermuda
group, which lies in the latitude of Charleston, S. C, about seven hundred miles from
Cape Hatteras, the nearest land. This reef is one of the most interesting, from the
fact that it is in the highest latitude in which corals are known to flourish with any
vigor, an exception whieli is probably the result of the sheltering action of the well-
known Gulf Stream. The most extensive coral plantations are found in the Pacific
and Indian oceans. On the eastern border of the former they are, however, very
insignificant. Worn fragments of coral are found on the Galapagos, and Col. Grayson

128 LOWER INVERTEBRATES.

mentions a beach of coral sand ou Socorro, one of the Rivillagigedo group. The
Sandwich islands are in part coralline. The Feejee, Pauinotu, Society, and Friendly
islands are composed wholly or in part of extensive coral banks. The coral sea along
the northeastern coast of Australia is the most extensive coral reef in the world. In
the Indian Ocean, again, we tind a large number of coral islands and reefs, among which
may be mentioned the Laccadives, Maldives, and reefs of the island of Madagascar.
Near the entrance into the Red Sea there occur coral banks of considerable size.

The part which the coral plays in the formation of the coral island has been vari-
ously estimated, and many opinions have been advanced in regard to this point. The
difficulty comes oftentimes from a lack of an accurate knowledge of the relationship of
the solid matter of the coral to the animal which secretes it. The carbonate of lime
which makes up the great mass of the growing coral bank is the skeleton of the
animal, and is simply a secretion of the membranes of the body. The skeleton cannot
be said to be the work of the coral, except so far as it is an animal secretion.

A growing coral plantation, with its multitudinous life, oftentimes arises from
great depths of the ocean, and the sea-bed upon whicli it rests is probably a submarine
bank or mountain, upon which have lodged and slowly aggregated the hard skeletons
of pelagic forms of life. When, tlirough various sources of increase, this submarine
bank apj)roaches to the depth of from one hundred to one hundred and fifty feet from
the surface of the water, there begins on its to]i a most wonderful vital activity. It
is then within the l)athymetric zone of the reef-building corals. Of the many groups
of marine life « hich then take possession of the bank, corals are not the only annuals,
but they are the most important, as far as its subsequent history goes. As the bank
slowly rises liy their growth, it at last approaches the surface of the watei', and at low
tide the tips of the growing branches of coral are exjjosed to the air. This, however,
only takes place in sheltered localities, for long before it has reached this elevation it
has begun to be more or less changed and broken by the foi-ce of tlie waves. As the
submarine bank approaches the tide-level, the delicate branching forms have to meet
a terrific wave action. Fragments of the branching corals are broken off from the
bank by the force of the waves, and falling down into the midst of the growing coral
below fill up the interstices, and thus render the whole mass more compact. At the
same time larger fragments are broken and rolled about by the waves, and are eventu-
ally washed ujj into banks upon the coral plantation, so that the island now appears
slightly elevated above the tides. This may be called a first stage in the development
of a coral island. It is, however, little more than a low ridge of worn fragments of
coral Avashed by the high tides and swept by the larger waves — a low, narrow island
resting on a large submarine bank.

The second stage in the growth of a coral island results from the formation on such
a ridge as we have just described of a quantity of fine coral sand. In the grinding
of the coral fragments which lie upon the fixed j^ortion of the reef, a large quantity
of the finest sand is formed. This sand is sometimes held in a mechanical suspension in
the water, and in that way is transjiorted from place to place. It is generally swejit
along from the locality where it originates, and is ultimately, if not lost in ocean de])ths,
thrown up on the ridge of coral fragments which has been already mentioned. The
wind assists the waves, and, taking the sand which they cast from the waters, blows it
as it becomes dry higher and higher on the ridge. Thus we have formed the second
stage in the development of a coral island, which is sim]ily derived from the former by
capping the coral fragments which form the foundation with a layer of sand.

Alcijonimii, coik ijolyp, natural size.

CORALS. 129

As the amount of sand increases it collects in such quantities as to be a detriment
to the growth of the coral animals themselves. It covers not only the foundation of
the coral island but extends far and wide over the coral plantation upon which the
island rests, and tends to kill the great colonies of life by which this platform is peo-
pled. The part of the reef where the coral life still lives now retreats into the ocean
to the greatest possible distance from the sand.

The winds, tides, and rains continue the work which they have taken up. Ocean
currents, especially, perform a most important part in the many changes which take
place. The problem now becomes a geological one, and wholly independent of those
of animal life.

The continual wear and tear resulting from the erosion of the water on the coral
island in its second stage of growth is ever increasing the amount of broken fragments
near the low-water line, while the winds snatch the sand thrown up by the waves and
heap it into high banks, dipping invariably to the sea. Exposure to the air and other
causes now exert their influences upon it, and the coral sand is hardened into a soft
rock, the well-known coral rock of these islands. The island is now formed?
Not yet. To the stability of the precariotis foundation thus made few persons could
with im[)unity trust themselves througli a tropical hurricane. There are other changes
before the coral island becomes firm, and its career has just begun.

In the progress of time the processes of erosion go on, and the waves and rains eat
their way into the soft rock so that the island is honeycombed by the erosion. Once
more the rock is reduced to fine sand, and scattered far and wide over the submarine
flats. The softer, least consolidated layers of the rOck, which, from not being exi^osed
to the air, are below the harder, wear away faster than the upper strata, which are
thus broken off in large fragments. The products of the erosion are strewn far and
. wide over the coral platform, and heaped np into a new island, of a different form
from that which existed before. One of two things now takes place with the debris.
Either the sand is again thrown uj) on the forming island, to again harden into coral
rock, or it is swept over neighboring growing coral reefs, raising these one more stage
to the level of the surface of the ocean. The movement by the wind of this sand
upon a coral island of considerable size often assumes formidable proportions. The
constant winds on some coral islands, as the Bermuchis, heap the coral sand into dunes
of considerable elevation, which slowly move en masse, engulfiug everything which
lies in its path. One of the most interesting of these moving masses of sand is to be
seen in Paget Parish, in Bermuda. The sand on the south shore of this parish has in
its motion suggested the name of a " sand glacier," and for several years it was slowly
making its way inlan<l from the coast, covering to a considerable depth farms, and even
a farmhouse, in its course. Artiflcial means of staying its progress had to be resorted
to, and by planting trees in the line of its onward motion the progress of the sand was
stopped.

In sheltered coral lagoons, whose floor is formed of coral sand approaching the sur-
face of the water, or with but a moderate depth, the mangrove trees oftentimes furnish
a nucleus around which characteristic coral islands, known in Florida as mangrove keys,
are formed. A small mangrove, sending its root into the submerged sand, forms an
obstruction upon which catch floating seaweeds and similar organisms. As the man-
grove increases in size, and its sjireading branches send down rootlets which fasten
themselves more firmly in the sand below, the obstruction is increased in size, and the
island grows with every increment to its size, until eventually we see a coral island of
vol.. I. — 9

130

LOWER INVERTEBRATES.

peculiar character formed on the coral shallows and flats. This kind of coral reef is
very common in sheltered localities in the Florida waters.

A coral island, however formed, is continually changing its contour, on account of
the method of its formation and the liability to erosion of the soft rock of which it is
composed. A study of the causes of the different shapes which coral islands assume
is highly interesting and instructive. In some cases their outline is due to the changes
in level in the foundations upon which they rest, elevation, and subsidence of the sea-
floor; in others to the direction of oceanic currents of the waters out of which
they rise.

Coral islands have every variety of form, although elongated, circular, ring-shaped,
and crescentic forms predominate. A coral formation skirting the shore, called a
fringing reef, follows the contour of the coast except when the continuity is disturbed
by local causes. The same may be said of reefs separated from the coast line by a
lagoon, and known as barrier reefs.

Circular or crescentic reefs are the most striking in shape, and their mode of for-
mation has been a cause of considerable speculation. The circular reefs are known as.

Flo. lJ.i. — Kuig-sbapetl coral island or atoll.

atolls, and are abundant in the Pacific and Indian oceans. Several atolls also occur
in the Atlantic and the Gulf of Mexico, of which the Marquesas Islands in the Florida
reefs is a well-known example. The Bermudas are, I think, erroneously ranked a&
atolls by many authors. From circular reefs, or atolls, to the simple elongated or
crescentic coral island we find every form of ring-shaped islands. There is nothing to
show that all circular coral islands are formed in the same way, or owe their peculiar
outlines to identical causes. In some cases they result from a sinking of the sea floor,
and in others from the direction of ocean currents in their immediate vicinitj'.

Many coral atolls have been shown by Darwin and Dana to have been caused by a
slow sinking and corresponding growth of corals on a submarine base. Let us suppose
an island favorably situated for coral growth to have a narrow, fringing reef around
its coast. Suppose also that in the geologic changes of the sea floor this mountain is
slowly sinking below the level of the sea. As the mountain settles the animals on the
fringing reef cause it to rise, /xwj passii, with the depression. The intensity of coral
growth is always at the periphery of the fringing reef on the side turned away from
the island, and exposed to the pure sea water. Tliere the coral formation, by the
growth of the animals, is kept to the sea level, iiotwithstjiiding the sinking of the

CORALS.

131

islantl. The first effect of the sinking island api:)ears in the formation of a higoon be-
tween the j)eripliery of the reef and the coast Hne. This lagoon grows in width as
the island sinks, while the constant growth of the coral on the outer rim keejis it at
the sea level. The submergence does not stop until the top of the mountain sinks
below the waves, but even then tlie outer rim, the peripheral edge of the original coral
reef, still holds its place at the water's surface on account of the correspondinn- <i-ro\vth
of the corals at that point. The island has now a true atoll shape, a ring-shaped reef
of slight elevation above the sea level, with a diameter equal to that of the base of
the mountain when the submergence began, — the diameter, of course, measured be-
tween points which lie in the coralline zone of the island. In this way, yet more
graphically, Darwin has explained the circular form not only of true atolls but also of
many curved or crescentic islands, such as are very common in the Pacific and Indian
Oceans.

Many objections have of late been urged against this theory of Darwin, and prob-
ably other causes must be sought for to explain the circular outlines of many other
reefs which have the form of true atolls. Semper has suggested the direction of ocean
currents as an explanation of the circular reefs of the Pelew grouji. Let us see if a

Fig. 123. — Island with fringing and barrier ret-ls.

similar cause cannot be found to account for the ring-shaped islands of the Atlantic
Ocean and Gulf of Mexico.

Every one who studies a good map of the coral islands of southern Florida will
have his attention attracted to the general trend of a long series of islands exteudhig
westward from Cape Florida into the Gulf of Mexico. He will perhaps notice that
these islands are very narrow in a north and south direction, and elongated from east
to west, strung along one after another in an almost direct, yet slightly curved line.
About midway in the chain, however, there are a few marked exceptions to tliis
general law, and these include some of the largest members of the group known
as the Pine Islands. Upon one of these islands, called Key West, is situated. a large
city of the same name. Unlike the other islands of the chain, the longer axes of the
Pine Islands, as pointed out by L. Agassiz, extend north and south, or at right angles
to the others. As a general rule, all the Floi'ida Keys are low, foi'ined of coral rock,
without caves of any size, and have no red soil, a characteristic of worn and eroded
coral islands. Their highest altitude, nowhere more than a few feet, is on their
southern border, and parallel witli them tliroughout their whole course runs a coral
reef, sej^arated from them by the Hawk's Channel, which is a half-dozen miles broad in
its widest part. South of the reef, which is a succession of dangerous coral banks

132 LOWER INVERTEBRATES.

and small islands, the water becomes deep, forming a trough for a great oceanic
current, the Gulf Stream, whose floor at this point is called the Pourtales Plateau.
South of this i>lateau is the deepest water of the stream which flows hard by the
neighborhood of Cuba.

The cause of the general trend of the Florida Keys must be looked for in the
direction of the Gulf Stream, or of a current flowing below it in an o])posite
direction, of which they were once the northern bank. This " oceanic river " flows
tangentially to the Florida reefs throughout their whole length, and to it may be
traced the general trend of the Keys from the Tortugas to the southern extremity
of the peninsula of Florida.

The exceptional position of the longer axes of the Fine Islands is directly due
to the Gulf Sti-eam and tide currents about them. The submarine elevation or jjlateau,
upon the southern border of which the Florida Keys lie, has not the great depth of
the Gulf of Mexico or the Gulf Stream bed between Florida and Cuba. On this
comparatively shallow jilatform the water rises in tides twice every twenty-four hours,
and at times, especially on its western extremity, the waters of the Gulf Stream are
forced over it. The water, thus raised above its natural level, must return to deeper
channels ; and one course which it may take is into the trough of the Gulf Stream
at right angles to the direction of its flow. The Pine Islands have their longer axes
tangential to several of these subordinate brandies or currents. A similar ])henomenon
is also seen in the channels which separate many of the Bahamas. The last but one
of the grou])s of coral islands which compose the Florida chain, which is called the
Marquesas, has a circular or atoll-like shajie. In this group we have a resultant of two
currents, or a combination of those minor currents which placed the axes of the Pine
Islands north and south and the Gulf Stream which gave the general trend to the
chain. From the position of the group near the extreme western end of the series
looking out into the depths of the Gulf of jMexico, these forces are difficult to separate,
and at intervals reinforce each other. The circular form of jMarquesas is due to their
combined action.

We have now arrived at a point in our discussion of coral islands where it
may be possible to appreciate the influence of ocean currents in the formation of atolls.
Let us consider the cluster of islands which occupies an irregular triangular space
midway between the southern point of Florida, the Bahamas and the island of Cuba.
This comparatively small coral bank is known as the Salt Key Bank, a coral plateau
which lies in the eddy of three great ocean currents. At most points the bank has a
moderate depth below the surface of the ocean, but in places along its outer rim there
are several coral islands of moderate size, some in process of formation, and others
whicli show the marks of great erosion. The Salt Key Bank, as far as it has been
explored, is a circular coral bank, fringed by islands which are not eontinuo>is above
water along its border, but which, nevertheless, are parts of a true atoll. On its sides
Salt Key Bank is washed by ocean currents, on the north Ijy the Gulf Stream, to
which the Florida Keys owe their formation, on the east and south to the Bahama
current in the old Bahama channel. Coral islands, as pointed out by Semper, form
tangentially to the dii-ection of ocean currents, and the outlines of the Salt Key Bank
result from the direction of the three currents which surround it.

There are few evidences of submergence in the Salt Key plateau, and if we cross
the Bahama channel to Cuba we find teri-aced coral banks elevated above the sea,
showing a great elevation of the coasts. The Salt Key bank, as well as the Florida

CORALS. 133

reefs and the Bahamas, are explicable without any theoretical supposition of submerg-
ence or elevation of the foundation upon which they rest.

The origin of an atoll in mid-ocean where currents are not confined as in the
triangle between Cuba, Florida, and the Bahamas, presents a similar although
somewhat modified problem. Let us supjjose a submarine mountain situated in mid-
ocean upon which for ages has rained successive depositions of sediment from the
watei's above. This sediment is composed in ]:)art bi shells of pelagic animals, and
plants, with which the waters of the trojiics or currents from the same are filled.
E\en at the greatest depths life exists upon such a bank, and tlie hard portions of the
animals which live and die there are being continually added to a growing submarine
bank. By increments made for many years the bank slowly rises to the surface of the
water. As it rises higher and higher the activity of the life on its crest increases, and
when it rises into the l)athymetric zone of the reef-builders, between one hundred
anil one hundred and fifty feet below the surface, a more rapid growth awaits it.
The coral plantation as it develops is washed by an ocean current, jDrobably on one
side. Such a current in fact is divided by the bank, so that each of the bifurcations
flow tangentially along its sides. It is evident in the first jslace that it is around the
border of the bank washed by the current that the most active coral life is to be
looked for, and in this region also that the predominant upward growth must be sought.
If the bank with which we started from the sea depths is circular the resulting atoll
will have the same form, and the part which first raises itself above the water will be
ring-shaj)ed, containing a central lagoon.

The luxuriance of the growth of the animals, 'which form a coral reef, is directly de-
jiendent upon the amount of food which the oceanic currents bring to the growing col-
onies. The waters of the ocean are filled with a wealth of microscopic and other life
floating in it upon which the living coral animals feed. It is evident that the possibilities
of jirolific cor.al life are greatest where their food is most abundant, and there too we
must look for tlie greatest amount of coral growth. It is clearly in the line of ocean
currents that this food, being constantly renewed by the flow of the stream, is most
abundant, and along its borders the possibilities of the coral animals of obtaining their
food are the greatest. This cause alone is not capable of determining the outlines of
coral islands, but it is a most important factor in regulating their growth.

Coral islands in two different conditions ought to be mentioned. We have coral
islands in process of formation, and those in conditions of destruction bj- erosion. The
Florida reefs are examples of the foi'mer, the Bermudas of the latter. Coral islands,
in progress of formation, seldom rise to any great height above the ocean, are composed
of coral fragments, sand, or half-formed coral rock. They are but verj' slightly eroded,
have no extensive caves with stalactitic formation, and no red soil. Fully formed
coral islands in which the erosive power of the water lias had its full effect are gen-
erally elevated, honej^-combed throughout by caves, and possess a soil of red earth.
This last characteristic of coral islands in the progress of erosion is of a problem-
atical nature and origin. By some authors it is regarded as the hca\-ier residuum
resulting from the wearing away of the coral rocks, while others have even gone so far
as to look upon it as the excrement of birds, mingled with coral sand. The former
theory seems most rational, but there is, if tliis theory be adopted, great difficulty in
accounting for its rechlish color. Red soil is very abundant in the Bahamas, the
Bermudas, and several of the West Indian islands. In the Bermudas it is contained
in pockets in the rocks, and in it are grown the well-known early vegetables, potatoes

134 LOWER INVERTEBRATES.

and ouious, for which the islands are so justly famous. In some places in the latter
islands it is found solidified into a coniijaet red rock in which are found embedded
Helices, and other shells belonging to species which are at present alive in Bermuda.,
The caves of coral islands are sometimes of most beautiful character and of consider-
able size. In the Bermudas most of these caves have a submerged floor in which ia
manv cases is sea water which is sensitive to the tides in the neighboring ocean.
Caves in coral islands present many very beautiful examples of stalactitic and stalag-
mitic formation. Many of the stalactites appear to extend from the cave-roof below
the level of tide water, indicating either a wide spread or local sinking of the cave-floor.
Of the many beautiful effects of the erosion of the sea water on cliffs of coral rock,
one of the most interesting is the formation of natural arches and the like out of spurs
of the hills projecting into the sea. In the neighborhood of a small Bermudian vil-
lage called Tucker's Town there is a very fine natural arch which bears a remote resem-
blance to the famous Arco Naturale of the Island of Capri in the Bay of Naples. A
similar arch called the " glass window " is found in the Bahamas.

J. Waltee Fewkes.

ECHINODERMS:

135

Branch IV. — ECHINODERMATA.

The animals embraced in this grouj) were iiichided by Cuvier in his great division
•of Radiata, along witli the coelenterates. More complete knowledge of the anatomy
and especially the embryology has shown that the two groups have nothing in com-
mon, except those features which are common to all Metazoa and the absence of a
segmentation of the body. The radiate arrangement, really a feature of minor
imjjortance, is here very strongly marked in most forms, for crinoids, star-fishes, and
serpent-stars have a central disc wdiich branches into five or more arms, which radiate
from it like the spokes of a wheel from the hub. In the sea-urchins and holothurians
this radial sj'mmetry is less marked, but it may readily be traced, although the radiat-
ing arms are apparently lacking.

Though at first sight widely different, the similar structure of a star-fish and a sea-
urchin can readily be traced. Let us first examine that of the first-named form. We
have a central disc with five radiating arms ; in the centre of the lower surface of the
disc we find a mouth, hence this is called the oral surface. On the upper or abora)
surface we find no opening (or only a very minute one), but a little one side of the
middle, between the bases of two of tlie arms, is a round plate, wliich, from its pecu-
liarly ornamented appearance, has received the name of madreporic body, in allusion
to its resemblance to
some of the corals. On
the under surface of
each arm will be found
a series of plates, be-
tween which project
little tubular suckers.
As these sucking tubes
are used in walking,
they have i-eceived the
name ambulacra, while
each of the series of
plates between which
they project is known
as an ambulacral area.

Turning now to the
sea-urchin, we find a
nearly spherical body.
On the under side we
have a mouth, from
which radiate a series
of plates, between
which project ambu-
lacra very similar to
but longer than those of the star-fish. These rows of plates continue around the
sides of the sphere, and terminate near the centre of the upper surface, where we

Fig. 124. — Aboi-al surface of sea-nrcliin {Arhackt); a, !>nal plates; c, ocular plates,
i), ambulacral area; o, madreporic body; 1, 2, 3, 4, 5, the five r.ays.

136

L 0 WER INVER TEBRA TES.

find a inadrcporic body like that of the star-fish. It is thus evident that these rows-
of plates eorresiwnd to the ambulaeral areas of the star-fish, and we can readily see
that were we to ln-nd the arms of the latter form ujnvards, so as to form a hall (most

i ^5^^ it;

Fig. 125. — Anatomy of st.ar-flsh; a, duct from liver to stomach; I', liver; c. inadreporic body;
j, ainpuUre; /, ambulaeral plates: m, iiUer-ambulaeral plates.

of the upper surface disappearinti' durins;' tlie ojieration), the star-fish would be con-
verted into a sea-urchin.

The typical number of similar parts (ambulaeral and inter-ambulacral areas) which
go to ms!ke up EchinodeiMii is five, though frequently this number is exceeded. This
radial arrangement is also seen in some of the internal organs, but it is not visible in

ECHINODERMS.

137

the alimentary tract. Bilateral symmetry is not so evident in most forms, though
it exists in all, and in the young is especially well marked. The line dividing the
body into two similar halves passes through the centres of the madrej^oric body and
of the central disc.

The internal organs are far more complex than those of the coelenterates. The
most striking feature is that the digestive canal is entirely distinct from the body
cavity. In the higher forms this canal is tubular in form, and as it is much longer
than the body cavity, it is coiled in a spiral, which in all, except the serpent-stars, is
coiled from left to right. An anus is usually present. Usually there are connected
with the functional stomach a number of glandular pouches, which secrete a bitter
fluid, and a2:)pear to represent the liver of higher animals. Organs which act as teeth
are frequently present around the moutli.

The so-called water vascular system is com]ilex and peculiar, jircsenting several
interesting features. From the

under internal surface of the mad- /

reporic body a canal goes down to
a circular tube surrounding the
mouth. From the fact that this
canal contains lime in its compo-
sition, it is known as the stone
canal. From the circular circnni-
oral canal (ring canal) a branch
follows the centre of each anibu-
lacral area to its extremity. Con-
nected with these radial canals
are the ambulacra. These ambu-
lacra are arranged in pairs, and
consist of two portions; an outer
part terminating in a sucking disc,
and an inner sac known as an am-
pulla. Between the two a tube
goes to the radial canal. Another
feature is sometimes present. Arising from the ring canal are from one to ten sacs
known from their discoverer. Poll, as the Polian vescicles.

The physiology of this water vascular system is not clearly understood. All that
can certainly be said ,is that by the action of the muscular walls of the ampuUte and
the Polian vescicles wAter is forced into and withdrawn fi-om the tubular ambulacra,
thus extending and retracting these organs. In the extremity of each ambulacrum
is a calcareous plate, to which are attached minute muscles, which by drawing in the
external integument form a vacuum similar to that which a boy forms with his wet
leather disc and a string. The strength with which these minute feet will cling is
remarkable, and the long stalk of the foot may frequently be torn in twain without
detaching the foot from the object to which it has become fastened.

Connected with this water vascular system, which is locomotor and possibly also
respiratory, is another which is regarded as the true vascular or circulatory sys-
tem. It consists of two rings, one surrounding the mouth, just below the ring canal,
while the upper surrounds the anus at the o]iposite pole of the body. These two
rings give off branches, and are connected by a tube which follows the course of

Fig. 126. — Diagram of water vascuLir system of a star-Iisb; a, mad.
reporic body; b, stone camil; c, ring canal; r/, radial canals
e,/, ambulacra and ampulla; (a few only shown).

138 LOWER INVERTEBRATES.

the stone canal. Regarding the functions of this system opinions differ greatly.
Some consider it as a true circulatory system, the tube connecting the two rings being
regarded as a heart, and described as pulsating in life. Perrier, the French authority
on these forms, on the other hand, regards the so-called heart of the star-fishes, brittle-
stars, and sea-ureluns, and the corresponding dorsal organ of the crinoids, as glandular
and the connecting branches as ca'ca.

The nervous system consists of a ring around the mouth from wliich radial branches
follow the course of each ambulacral area. Subdivisions of these princijial nerves
sujiply the ampulla, ambulacra and other parts of the bod}-. The only sense which
appears to be present in all of the group is that of touch, for whicli various external
parts are well adapted. In some of the star fishes and sea urchins rudimentary eyes are
found at the extremities of the ambulacral areas, whether at the tip of the arms or at
the corresponding position on the aboral surface. (Fig. 124, c.)

The external covering varies greatly in the various forms, but plates of carbonate
of lime are usually present. These plates may be firmly united so as to form a solid
shell, or they may be separate and imbedded in the integument. In some the}' lU'iy
take the form of spicules, wheels, and anchors, those of Chirodota and Synapta being
familiar objects to all workers with the microscope. In the star fishes these plates are
very numerous, two series roofing over the ambulacral groove in which the sucking
feet are situated. In the serpent stars the ambulacral plates occujiy the interior of the
arm, which is entirely surrounded by a series of plates. In most of the sea urchins
the plates of the ambulacral and inter-ambulacral areas unite to form the solid test in
which the body is usually enveloped, the surface of which is covered with little
rounded prominences for the attachment of spines. In the crinoids the calyx and the
jointed stalk and arms are largely composed of calcareous matter.

Spines, often varying greatly in size in different jiortions of the same individual,
are widely distributed among the Echinodermata, most of which also possess certain
fork-like or piucer-like organs, which are modified spines, and which from being
stalked in some forms are known as pedicellariffi. These are capable of closing and
seizing any object which may come between their jaws, and are supposed at least in
some forms to take the excrement from the anus on the upjier surface of the body,
and pass it along, off from the shell to the ground.

The sexes of most echinoderms are separate, and the genital products are discharged
either by a breaking away of the integument or by true genital openings. The
young of most of the branch undergo a wonderful metamorphosis in the course of
their develojjment, and tlie embryos are free swimming animals. The ' jiluteus ' of
the sea urchin, the 'bipinnaria' or the ' brachiolavia ' of the starfish, and the ' auricu-
laria ' of the holothurian, bear no resemblance to the adults, and in fact the name now
applied to these larv£e were originally given them under the impression that they were
adults. In certain groups the embryo develojis into the adult without any metamor-
phosis. As there is such variation among the different groups we will defer the
details of development until treating of the respective forms.

The Echinodermata are all marine, and are found in all the seas of the globe. If
ancestry confers respectability these forms should be classed among the nobility, for
remains of these animals are found in some of the oldest fossiliferous rocks. At the
present time they Jjlay an unimjiortant jiart in the economy of the world, and are of
but slight importance to mankind. A few forms are used as food, while others are
injurious to human interests, as they destroy beds of oysters and other shell-fish.

CRINOIDS. 139

Class I. — CRINOIDEA'.

The lowest division of the echinoderms and at tlie same time the one wliich has
the fewest recent representatives is the Crinoidea. The fossil forms of tliis class are
very numerous in the older rocks, and are commonly known as encrinites and stone-
lilies. The recent forms are so little known and so seldom seen by any except those
wlio are familiar with the results of dee])-sea exjjlorations that they have received no
common name. The greater portion of the sjjecies are attached to sub-marine objects
by a stem which, frequently, is very long, and made up of a scries of joints perforated
by a central canal. These joints are among the most numerous fossils in the older
rocks, and have received the name of St. Cnthbert's beads. This stem supports a
calyx (corresponding to the central disc of the star-fish) which has received its name
from its similarity to the calyx of a flower. From this calyx radiate the arms. Some
forms have the stalk persistent througliout life, while others jiossess it only in the
early stages, and in a few fossil forms it is said to be lacking in all stages.

The class is usually divided into three orders, the Blastoidea, the Cystidea, and
the Braehiata, or true crinoids. The first of these is extinct, the second contains one
recent form, and the third, until recently, was thought to be represented, with
one exception by free swimming forms. The recent deep-sea cx]>Iorations liave,
however, brought to light several species, some of considerable size and others much
smaller than some of the fossil forms.

Order I. — BLASTOIDEA.

The members of this extinct group of Crinoids were armless, were su]iported on a
short stalk, and had five double series of pinnules, one along each side of five radiating
grooves. The entire animal, in its fossil state, with the oral plates closed, looks like
a flower-bud. The most ancient form {Pentremites) is found in rocks of upper Silu-
rian age, and the group is most abundant in the carboniferous.

Pentremites has the ambulacral and ant-ambulacral regions nearly equal. The
calyx is composed of three basal plates, two of which are double. Above tliese lie five
plates deeply cleft above, and in the clefts lie the apices of the ambulacra, the oral
portions of which are included between the five interradials which surround the cen-
tral aperture. This is probably the mouth, and around it are four double pores, and
a fifth divided into three. Of these three the middle one is believed to be the anal,
while the other two, and the remaining pairs are genital. Each ambulacrum consists
of two rows of small plates which are united in the middle line, and bear pinnules at
their outer ends.

Order II. — CYSTIDEA.

The Cystidea come near the crinoids, are usually furnished with arms, having
jointed pinnules, and have a short stalk. Caryocystites has no stalk and no arms, the
body being an angulo-sjiherical ball of solid jjlates. Several genera {Edrioaster,
Agelacrinites, Ilemkystites), are also armless and stalkless, but in form resemble such
a star-fish as Pterastei; except that they are more nearly circular. These forms have
five ambulacra, looking like the arms of an ophiurid placed in the midst of the disc,
and, like the more normal stalked cystid, they possess, in one of the interambulacral

140 LOWER INVERTEBRATES.

spaces, a cone of small plates called the pj'raTiiicl, witli a central aperture. In ordi-
nary cystids, pinnules are present, which, when the arms are absent, are sessile on the
radial plates. An aperture placed in the centre of the calyx at the point of convei'-
gence of the aml)ulacra, is usually regarded as the mouth ; a second small one on one
side of this is sujiposed to be the anus ; while the opening in the centre of the pyramid
is considered to be the reproductive aperture. Thus the Cystidea differ from other
echinoderms, the holothurians excepted, in the presence of only one genital aperture.

Ilyponome sarsii, from Torres Strait, looks like a small star-fish or Euryale. It
has a disc, convex on the oral surface, and flattened on the other, which shows no
trace of a calyx, but is covered Avitli a soft and smooth brownish skin. The rays are
five, broad and short, yet each divided into two branches, ending in four very short,
rounded lobes. The oral surface is covered with rather small, thick-set, irregular
scales, with rosettes of six or seven larger ones here and there. These scales extend
on to the dorsal surface between the rays, forming triangular spaces pointing to the
centre of the disc, and thus reducing the spaces covered by skin to a regular star.
The rays have narrow channels, protected by marginal scales, but have no pinnules.
Upon the disc the marginal scales form a vault over the channels, and the mouth itself
is hidden by the skin. There is a conical anal funnel in one of the inter-radial spaces
on the oral surface, and an area in the middle of the dorsal surface is studded by
minute pores. Funnel-like passages leading to a concealed mouth are found in jjalas-
ozoic Brachiata and cystideans. The absence of a calyx excludes Ilyponome from
the former; and it in some respects recalls the genus Agelacrrnites among fossil
cystids.

In op])osition to the usual idea about these fossils, Mr. Billings maintains that the
large lateral aperture of a cystidean is the mouth, and the small apical orifice an
ambulacral ajierture. When there is no separate anal aperture, the large lateral a]ier-
ture is both mouth and anus.

The Cystidea first occur in the cambrian, attained their greatest development in the
Silurian, and were mostly extinct in the carboniferous period.

Order III. — BRACHIATA.

This order was represented by a multiplicit)' of forms in the past geological ages,
and has latterly been shown to be far more abundant in species in the present age than
was supposed. As the name implies, all the species are provided with arms. These
arms are composed of numerous calcareous joints, and contain only a small proportion
of living matter. Existing crinoids belong to two distinct series. The first of these
contains forms which are permanently attached by a stalk to the sea-bottom, while the
second is thus attached while young, but finally becomes detached, the cup or calyx
with its arms and a pear-shaped centro-dorsal tuliercle, foi'med of the coalesced upper
stem-joints, floating off freely. In this stage the animal greatly resembles a star-fish
in appearance, but its anatomy is very different. The stalked crinoids, which are prin-
cipally natives of deep water, may be considered as the representatives of the extinct
stone-lilies, while those which become fi'ce belong to a more recent and more highly
developed type.

The characters which distinguish the crinoids from other echinoderms may be
briefly summed up as follows: Tlie animal is attached, during the early portion or the
whole of its life, by a stem composed of more or less numerous joints. To the to]i of

CRINOIDS.

141

the stem are attached a variable number of plates, normally including one or more
basals, and three or more sets of radials, which, with interradials, etc., make up a cup
or calyx in the hollow
of which the internal
organs of the animal
are accommodated.
From the edge of the
calyx spring a number
of jointed arms, usually
five, these again divide
once, twice, or more
times, and each arm is
furnished with pinnules
as a feather is set with
barbs. The ambulacral
feet are situated in the
furrows of the calyx and
along the arms. No
other echinoderms are
fixed at any period of
their life-history ; in no
others do the arms sub-
divide into pinnules,
and in no others is the
madreporic plate ab-
sent, though in most
holothurians it is in-
ternal. The mouth is
situated in the centre
of the upper side of the
calyx, instead of in the
centre of the lower side
as is the case in star-
fishes and sea-urchins,
while the anus is placed
on a conical projection
between the bases of
two of the arms. It is
thus probable that the
upper surface of a
crinoid is homologous
with the lower surface
of a star-fish or sea-
urchin. The oesopha-
gus is short, and the in-
testinal canal is more or less coiled in its passage to the anal extremity.

Fig. 127. — Antedon on the tube of a worm.

The

mouth does not contain any masticatory apparatus, comparable with the so-called
'jaws' and 'teeth' of sea-urchins and serpent-stars. The upper surface of the

142 LOWER INVERTEBRATES.

calyx is more or less covered over by the oral plates, usually five in number.
These are separated by naiTow spaces that are continuous with grooves that run
along the upper surface of the arms and pinnules. The water system is upon the
usual echinoderm plan, that is, a ring around the mouth, and radial vessels running
along the arms. The ambulacral feet upon the oral surface of the calyx are connected
with the ring canal. The body cavity extends into the arms, which also contain the
greater part of the ovaries, as in the star-fishes.

In Antedon and other free crinoids there is a cavity known as the chambered
organ, which has its walls and floor formed almost entirely l)y the centro-dorsal tubercle,
and therefore, by what was once a stem segment. This chambered organ is rudimen-
tary in the cystidean or unarmed phase of growth, but becomes developed as the coma-
tula acquires arms and cirri, and is connected with these jiarts by fibro-cellular cords
in the axis of the calcareous part t)f the arms and cirri. These cords are believed to
be nerves, and the chambered organ must therefore be regarded as the centre of the
nervous system. The ' ovoid gland,' which some consider to be a heart, is implanted
on one of the horizontal floors of the chambered organ.

In Pentacrinus the chambered organ is a part of the central space enclosed within
the jientagon formed by the radials and basals, while in the Apiocrinidte {Shizocrinus
and its relatives) an intermediate condition exists. The ovaries (in Antedon) dis-
charge their ova from openings on the arm pinnules. The eggs are fertilized while
attached to the exterior of the opening, undergo total segmentation, and after awhile
develojj into oval embryos with a surface covered with cilia. When the embryo leaves
the egg, it is girded with four zones of cilia, beai'S a tuft of cilia at one end, has a
mouth (surrounded by large cilia), and an anal opening, and is free-swimming. In a
few hours or days, traces of the calcareous plates, destined to form the cup of the
future crinoid, begin to appear; then the plates of the stalk develop, and lastly the
basal plate. As is the case with all echinoderms, there is little in common between
the larva and the young of the perfect form. The young crinoid is formed within the
larva, and the mouth and digestive cavity of the latter are not converted into those of
the former. Two or three days after the appearance of the 23lates, the larva begins to
change its form, the cystid-like young crinoid is seen embedded in the body of the larva,
and the latter sinks to the bottom and adheres to some object. The stem becomes more
elongate, while the part which will be the calyx still remains short and thick. The
broad end of this part becomes five-lobed, each lobe answering to an oral plate, and
these plates open like the petals of a flower, showing the oral aperture. Tentacles
then appear between the oral plates, eventually arranging themselves in groups of
three. Alternating with the basal and oral ])lates, the five radial plates now appear,
and the arms grow out rapidly. The calyx also widens, so that the oral plates be-
come widely separated from the basal, which encircle the stem. The alimentary canal
of the young crinoid, which has before been a mere sac, now develops an intestine
which opens out on an interradius where an anal plate has now ajipeared. If tlie ani-
mal is a stalked crinoid, the principal further external alterations are the acquisition
upon the stem of whorls of cirri at intervals, the bifurcation of the arms, and the
development of pinnules upon them.

In Antedon or Comatula, Actinometnt, and Atelecrimis, foi-ming the family Coma-
TViADM, the young are stalked and attached, but the calyx, together with the upper-
most joints of the stem, breaks off at a more advanced period of life, and the crinoid
swims off freely. Articulated to the lower or aboral face of the centro-dorsal tubercle

CniNOIDS. 143

formed by the upper stem-joints are the numerous cirri with whicli the animal grasps
bodies to which it may desire to become temporarily attached. There are five series
of radials, each containing three ossicles. Tlie first or lowest three are closely
adherent to each other and to the centro-dorsal tubercle, which conceals them on
their outer side. That the central ossicle with the cirri is not the true basal plate
is proved by the presence on its upper surface of a basal enclosed between the apices
of the first three radials. This basal plate, called the rosette, is formed by the
coalescence of the five basals of the larva.

The alimentary canal makes about a turn and a half round the axis of the body,
and ends in the projecting inter-radial rectal cone. Included within the coil of the
alimentary canal is a sort of cone of connective tissue, which has been called the
columella. The five oral valves contain no calcareous plates in Antedott. The posi-
tion of the genital glands in this and other crinoids, namely, in the i)inuules, seems
very exceptional, yet they are lodged in tissue, which is a continuation of the cellular
tissue of the arms, comparable to that in which the ovaries are lodged in star-fishes.
The species of Comatulaj are numerous. The " Blake " expeditions have latterly
added forty to the twenty ])reviously known from the Caribbean Sea, and about
seventy were dredged by the " Challenger " between Cape York and the Philippines,
and thence southward to the Admiralty Islands.

The chief distinctions between the two principal genera are as follows : — In Ante-
don the mouth is central, or sub-central, and the ambulacra are equal, the arms are
equal in length, grooved, and furnished with tentacles. Red spots, tlie nature of
which is unknown, and which are absent in Actuiometra, are always present at the
sides of the ambulacra. The cirri are numerous, and more or less cover the centro-
dorsal tubercle, and the outer faces of the radial plates are relatively high, and inclined
to the vertical axis of the calyx. In Actinometra the mouth is not in the centre of
the disc ; the ambulacra are variable in number and unequal in size, two of them
always forming a horse-shoe round the anal area ; the pinnules of the mouth have
combs at their tips ; some of the hinder arms may be shorter than the others,
ungrooved, and without tentacles ; brown spots, thought to be sense-organs, may be
present on the dorsal side of the pinnule segments ; tlie cirri are few ; and the outer
faces of the radials ai-e wide and parallel, or nearly so, to the axis of the calyx. In
Antedon the ambulacra of the ]iinnules may be protected by side-plates and covering-
plates, but these are absent in Actinometra.

In the Caribbean Sea Actinometra is represented by more species and more indi-
viduals than Antedon, and two-thirds of the species of the latter and three-fourths of
the former have ten simple arms. In the remaining species the rays rarely divide
more than twice ; only two species divide four times. Antedon and Actinometra are
about equally represented in the eastern seas, but while half the species of the former
genus are ten-armed, oidy three Actinometrm are thus simple. Nearly all the ten-
armed Actinometra;. of the eastern seas have the second and third radials unite<l by a
double joint, without muscles, called a ' syzygy,' and each of the first two brachials
is a double or syzygial joint. But all the ten-armed Actinometrce of the West Indies
have the second and third radials joined by ligament, while the first syzygy is on the
third brachial.

The two Comatulfe, which, from their abundance, seem to specially characterize
the Caribbean Islands, are Antedon spinifera and Actinometra jndchella. The first
has usually thirty arms, but occasionally forks four times. The disc bears a tolerably

144 LOWER INVERTEBRATES.

complete plating, and there is a double row of plates along each edge of the pinnule
ambulacra, which are thus covered over. The spread of the arms is about eight
inches. Actinometra pulchella varies greatly. The arms may be ten, twelve, or
even twenty. The mouth is far out of the centre, and the disc is bare, or more or
less covered with calcareous plates. It is about ten inches across the arms.

Atelecrinus, of which two species, ctcbensis and halcmoides, are known, has the
first radials visible, and separated from the centro-dorsal tubercle by a complete circlet
of basals. No other Comatula, with one doubtful exception, retains its embryonic
basals on the exterior of the calyx after the latter part of its existence as a Pentacri-
noid, and no other Comatula, recent or extinct, has a complete basal circlet of live
pieces.

In A. balanoides the acorn-shaped centro-dorsal is marked all over by the horse-
shoe-shaped sockets of the cirri. The tirst ten or twelve of the arm-joints are with-
out })innules. In the characters of the calyx Atelecrinus is a permanent larva.

The Comatul;^ dredged by the "Blake," were nearly all taken in depths less than
•200 fathoms; and as the "Challenger" only found Comatulas at greater depths than
this on twenty occasions, P. H. Carpenter concludes that the group is essentially
a shallow water one.

We now come to the stalked crinoids, which, though they so long eluded search,
are not really abyssal forms, since they have on only fourteen occasions been dredged
from depths exceeding 650 fathoms.

Pentacrinus has a long stem, bearing whorls of unbranched cirri at intervals, and
lives attached to rocks in moderate depths. The joints of the stem are pentagonal.
There is no distinct basal piece to the calyx, and the arms bifurcate twice, thus giving
twenty principal free arms. The first forking occurs at the third radial. The ambu-
lacral grooves of the arms have a series of ossicles along their floor and lamellie along
their margin.

lu this genus the third radials, or radial auxiliaries, have their two sides bevelled off
like the eaves of a gable, to allow two joints, the first joints of the ten arms, to be
seated upon them. The first joints of the arms are split in two by a peculiar
joint called a ' syzygy.' The ordinary arm joints are provided with muscles for the
various motions, but the syzygies are not so provided, and consequently, when one of
the arms is entangled, or caught, it breaks off at one of the syzygies, a beautiful pro-
vision for the safety of an animal with so complicated a crown of appendages.

The stem of Fentacrinus consists of many flattened calcareous joints, the upper
and lower surfaces of each of Avhich show five radiating leaf-like spaces, each sur-
rounded by a border of tiny ridges and grooves. These ridges and grooves fit into
each othei-, so that, in spite of the number of joints, the motion of the stem is very
limited. The leaflet-like spaces thus come over each other, and five oval bands of
strong fibres pass right through the loosely-arranged calcareous network of these
spaces from one end of the stem to the other. There are no muscles between the
joints, so that the animal does not appear to be able to move its stalk at will. Each
joint has a hole in its centre, and this chain of holes is continuous with others which
run through to the plates of the cup, and continue through the axis of each arm, and
along every pinnule. In P. asteria about every seventeenth joint of the stem bears a
wjiorl of fine, long tendrils, or cirri, which start from shallow^ grooves in the pro-
jecting angles of the pentagonal stem. These cirri usually have thirty-six or thirty-
seven short joints, the last of which is sharp and claw-like. Though they have no

riiixows.

145

true muscles, they seem to have some power of eontraotinri; aroniul resistins; objects
which they touch. The <-irri beconie smaller anrl closer toe;ether near the head, for
each cirrus-beaviuji- joint develops immedi-
ately below the calyx, and the joints which
se])arate the cirrus-bearini;- joints from each
other develop afterwards.

In I*, (listeria the .arms divide a second
time .about six ai'm-joints above the first
bifurcation, and again bifiu'cate seven or
eioht joints farther, the bifurcations repeat-
iuu' themselves somewhat irregularly until
each of the primary arms has divided into
twenty or thirty branches, m.iking more than
a hundred arms in all.

JR. iri/ui7le-tho>iiS()/u\ fmind upon the
coast of Portugal, has the cirri separated
by thirty to tliirty-tive joints. The num-
ber of arms is not constant, because in
some cases the third radi.als bear one ov
two sini]>le arms, while in others there is
a third liifureation.

Some examples of J', miillrri, and .all <if
P. (ri/rilh-tliiiiiisoni, that wci'c dredged by
Mr. .Teft'rcys. showed by the smooth and
rounded terminal joint of the stem, by the
shortness of the lower cirri, and by the
small number of joints in the lower inter-
nodes between the cirri, that they must
have for a long time been free, and Sir
AVyvillc Thomson states his belief that
the latter species lives loosely rooted in
the soft mud, and can change its place at
pleasure by swimming with its j)iimatcd
arms.

P. luadeuricuiiig, dredged near the coast
of Brazil, has a peculiar style of arm-divi-
sion. Each of the ten primary arms stand-
ing upon the radial auxiliaries, gives off
two secondary arms close to its base, ,so
that there would be in all thirty arms, were
the arrangement absolutely regular. The
arms are very robust, and the joints have
a tendency to widen in the middle of the
arm. Each arm has about seventy joints.
The cirrus-bearing joints of the stem arc
very short, and much inflated with round, bead-like knobs, and there are only two
very thin plates between the nodes. Sir W. Thomson believes that this form floats
about unattached.

VOL. I. — 10

Flti. 128. — PcntacriitHS asfer!a.

146 LOWER INVERTEBRATES.

The most common pentacriuoid of the Cai'ibbcan .Seas is apparently P. decoriis, in
which the whole of the cirri are separated l>y ten to twelve internodal joints; the nodal
joints are laroe and jirojectinw, and the two outer radials, and the tirst two joints
beyond them are united by ligament, instead of by muscles or by a syzygy.

P. riitdleri, though confounded with this species by Thomson, differs widely.
The internodal joints of the stem, are only six or eight ; the cirri are stout, and have
about forty joints, the outer radials and succeeding joints are united by syzygy, as
in P. iDfterkt, and the arms fork much as in the latter. Eight species of Pentacrinits
are now known.

The most wi<lely distributcil, ami at tlic same time one of the simplest of living
crinoids is Rhizocrinus lofoteiiKis, a species wlndi dcics imt cxcceil three inches in
len^'th, and lives at depths of from one hundred to one thousan<l fathoms in the North
Atlantic, and u]i(>n the coasts of Florida. The stem is relatively lonu and many-
jointed, some of the basal articulations bear branched, root-like filaments, or cirri, and
at its sunnnit is a calyx consisting of a central piece or basal and five tii-st i-adials, all
closely united together and perched upon the enlarged solid, pear-shaped upper joints
of the stem. To these five first radials, follow two other sei-ies of radials, all included
within the calyx, but each following the line of an arm. To the third radials are
attached the tirst tii the ossicles of the unbranched but pinnule-bearing arms, which
vary in number from four to seven, and have fnnii twenty-eight to thirty-four joints.
The pinnules alternate with each other along the arms, and have also a jointed skele-
ton. The mouth is circular, but is surrounded by the five (or four) oral valves, which
close over it when shut. Between the circular lip and the oral valves there is a series
of soft, flexible, tentacles, two pairs to each valve. Tlie outer one of each pair is very
contractile. Tentacles of a similar character are continiietl along the deep grooves
which traverse the oral surface of the arms and ]>iimules.

P. rawsoni is readily known from the last species liy its more robust appearance
and elongated calyx, which is nearly always constricted at the suture with the radials.
The greater part of the cup in this genus is formed l»y the elongated basals, which, in
the Norwegian variety of P. h/oteiisits are so completely fused that no sutures are
visible, a peculiarity whicli led to the supijositimi that this jiait was formed of enlarged
upper stem-joints as in a Co/natiifa. P. i-aa-soni. is a larger form than li. lofotensis.

Hyocrinus hetheUianus has much the structure of the jjaheozoic Plati/crinus. It
has a rigid stem made up of cylindrical joints applied to each other by a close syzygial
suture. The cup consists of a basal ring which seems to lie formed of two or three
pieces, and of a tier of tine, thin, broad, spade-shaped ladials. The arms are live in
number, and are built uji of long, cylindrical joints. The tirst three joints consist of
two parts sejiarated by a syzygy, the other joints have two syzygies. From the third
and all sul)se(|uent joints s|>rings a i>innule, the pinnides alteiiiating on either side of
the arms. The lowest pinntdes are very long, the succeeding ones becoming shorter.

The outer jiart of the disc is jiaved with irregular closely-set plates, bounding the
five large orid valves. The ceso])hagus is short, and is succeeded by a stomach sur-
rounded by brown glandular ridges, the intestine is very short, and contracts rapidly.
Round the gullet a rather ill-defined oral ring gives off, opposite each of the oral plates,
a group of four tubular tentacles. This species was dredged near the Crozet Islands,
and also with BatJii/criniis, in eighteen hundred and fifty fathoms, off Brazil.

Holopits is a short, stout form with no true stalk, with a broad, encrusting base
instead of the branching cirri oi P/iizocrrnus, and ten arms which can be rolled together

LIVING CRINOIDS.
1. Rhizocrinus lofotensis. 2. Hiiocrinus betheUianus.

SERPENT STARS.

147

spirally in such a way as to enclose a close<l cliamlier between them. The pinnules are
formed of hroad, flat joints, and can be spirally rolled towards the arms.

In Holopus there is a marked divi-
sion into bivinm and triviuni, as in some
holotluirians, the three facets of the
trivium are larger than the other two
facets (the central one largest), and the
three arms attached to those facets of
the cup are larger than those joined to
the opposite side. Another attached
genus is Jidthycrhius, one species of
which was dredged with IIijuGviiins in
eighteen hundred and fifty fathoms, off
Brazil, while another was taken at two
thousand four hundred and thirty-tive
fathoms in the Bay of Biscay.

Class II. — STELLEKIDA.

The Stellerida are echiuoderms with
star-shapeil or pentagonal bodies, a well-
developed water system, and an internal
skeleton, consisting of ambulaeral plates
which are different from those of the
Echinoi<lea, since the nerve cords and
radial ambulacra! vessels lie outside and
below them. Tliere are two orders,
Asteroidea and Ophiuroidea.

Ordei; I. — ophiuroidea.

The Ophiuroidea ai-e a group of star-
fishes, characterized by a more or less
sharply-defined central disk, containing
a digestive cavity, which may l)e sim])le
or much plaited, but which does not
pass into the arras. Thei-e is no anal
opening. The arms have an axis com-
posed of calcareous o.ssicles, usually
called arm-bones, which greatly resem-
ble vertebra;, and each of wliicli is
made up of two sections. These two
sections represent the ambulaeral plates of ordinary star-fishes. The axis is cased either
with plates, or with a thick skin having rudimentary plates beneath, and the jilates upon
the sides of the arms usually bear s))ines. Within the hollow of the arm, covered by
the under arm-plates, yet in the same relative position to each other and to the ambu-
laeral ]>lates or arm-bones, that obtains in the true star-fishes, run the nerve, the neuval
canal, and the ambulacra] vessel of the water system. There are no ampullar in con-

FlG. 12f). — Bafhifcrinus altlrirkianus.

148 LOWER INVERTEBRATES.

nec-tioii with tlu' wator-feet, whicli ;\\x' siinplo tcMit;\i-li's without siu-lvi'vs at their ti]is.
They make their exit between the hiteral jihites of the arm-eoveriiiii-. Eaeh of the five
angles of the iiKiiith is funned of fi\e jiiect's. 'I'he two lialvesof one or twt) ann-lxmes
(Lyman says two, lieeaiise tliere are two soelvets for tentaek's) are modified into strong
iiiouth-franies, movalily articulated au<l swuiil;' apart from eaeh other. The extremities
of these mouth-frames are soldered to a jaw or iiiter-andiulacral jiiece, and to the inner
edges of eaeh jiair of jaws is articulated a long, nariMW jaw-]ilate, wliieh sujiiiorts a
variable numlier of i)roeesses, which are called teeth, and d(julitless serve the purjiose
of such.

On either side of the base of eaeh arm are tlu' radial shield abo\ e, and the genital
plate below. These are joined at tin/ maigin cif tlic disc, .ind cdimected by nn
adductor muscle. On the under side, in liie space between the ar-ius, are one or two
genital openings, paralk'l «ith and close tn I'ach arm. These, in thi' great majiiritv
of species, enter a jieculiar sac, the genital bursa, «ith which the tubes from the
ovaries or spermaries communicatt'. Apostolides considei-s that these bursa' should be
regarded as respiratory sacs, as they may be seen to .alternatt'ly contract and dilate.
Each inner angle of the numtli is usually co\'ered by .-i jilate, called the mouth-shield,
and one of these usually sei'ves as tiie niadre]>(>ric body.

The nervous ami circulatory systems, and arrangement of the water system, are
ujion the usual star-tish plan. The Ixidy cavity consists of an <'nlargt'd portion sur-
rounding the digestive tube, and a flattened ])ortion in the dorsal region. Tile nerves
have l)een found to contain cells with large miclei, somewhat resembling the ]iigment
cells of vertebrates, ami also delicate fibrils, with jiale, bi-]iolar cells not collected into
ganglia.

The Ophiuroidea fall into two f.amilies. In the lii'st and larger family, < )l'lliri£ll).E,
the axis of each arm is encased in a greater or less number of plates, the principal of
which, from their position, are known as the dorsal, ventral, and lateral jilates. The
lateral jilates bear a. more or less munerous series of s]iines, and are usually considered
homologous with the ad-ambulacr:il plati'S of the arm of an onlinary star-fish ; the ventral
and dorsal jilates are primarily un]iaired, and the former, at least, are iieculiar to the
group. 3[(juth-s]iields are always present, and there are often two other siqierHcial
plates, the side mouth-shields, one on each of the outer sides of each mouth-sliiehl.

The Ojihiurida' rarely have more than five arms, and these are in all cases
unbranched, but in the other family, the Astro] ihytidfe, the five arms usually divide
and sub-divide into a very large number of branches. TJie latter family is destitute
of the regular covering of jilates that jirotect the arms of the 0]ihiurida', but in its
place has a thick skin, under which are plates, usually of an iiri'gnlar and elementary
character. The arm ossicles consist of a vertical and a horizontal hour-glass-like pro-
jection, fitted one on the other. There are no siiincs on the sides of the ai-ms, and
mouth-shields are often absent in the hranched species, in which the niadre|ioi-ic jilates,
sometimes one and sometimes five in number, may be found in \.'irious jmrts of the
lower inter-brachial spaces.

The arm ossicles of tlu' Ophiurida', according to Ludwig, are originally double,
the first rudiment consists of two calcareous jiieces symmetrically placed on cither
side the middle line of the arm; each triangular jiiece is formed of three rays, two
directed orally, the third al) orally; the latter increases considerably in length, and the
two others gradually become fused together. Till a late stage of growth, there is in
the middle of the ossicle a sjiace with concave sides.

SEnPE.Xr STARS. 149

In typical Ojihiurans the mouth, just above tlie teeth, opens by a round, contrac-
tile aperture into a large, flattened jstoniaeh, which spreads over the basis of the arms
and into the inter-brachial spaces. Though sometimes a little wrinkled, it is usually
destitute of pouches, convolutions, or ceecal ajiiiendages. Jietween the stomach and
the disc wall lie the reproductive organs, consisting of elongated bags communicating
with closed tubes, wliich bear the ova or spermatozoa. In the Astrophytidte the
upper part of the stomach is surrounded by mnuerous radiating folds or bags, which
are attached to the roof of the disc, to the genital organs, and at ten points encircling
the mouth. The body cavity would thus be divided into ten parts were it not for the
open space or canal which runs around the mouth, and corresjionds to the ring-canal
of a true Ophiuran, l)ut differs in being a continuation of the l)ody cavity instead of a
closed, annular tube. There is no closed bag for the genital products, but the body
cavity is the genital cavity, and an ovarial lol)e opens into each comjiartment.

Lyman enumerates about five hundred s))ecies of ()pliiuroi<lea, forty-nine of which
are Astrophytiihe. .Vlllioiigli liut few of the sub-<ir(ler can lie reuarded as littoral,
more than half, or two hundi-ed anil seventy-eight species, are found above the depth
of 80 fatlioms, and two hundred and twenty-six of these do not occur in dee])er water.
Thirty-eiglit of the renuiiaing coast s]iecies do not deseend bevond ITilf fathoms,
twelve others reach to ;')()(!, .-md oidy two go lower than 500, but do not reach 1,000
fathoms. Between oO and loO fMthoms one hundred and fifty-one sjiecies occur,
sixty-nine of which are not founil cither above or below this range. Between 150
and 500 fathoms one hundred .-hkI thirty-seven species occur, seventy of which are
confined within these limits, while thirteen descend to below 1,000 fathoms, and
twenty to below 500. Only sixty-nine s]iecies' occur below 1,0(10 fathoms, and of
these fifty d<> not occur aliove that limit. This number may of course be increased
by subsecpient rlredgings, but even now we know of fifty exclusively dee])-water
sjiecies, living in water cold almost to freezing, and in entire absence of suidigiit.

In the genus Ophiura the disc is covered with small granulations, which more or
less covers the small, oblong, sejiarated radial shields; the jaws are set with teeth; the
spines, which are on the outer edges of the side arm-]ilates, and parallel to them, are
smooth, flat, and shorter than the arm-joints; side mouth-shields aiv ]iresent, and there
are four genital openings. A fine species is O. /r/v.v, from Lower California and the
west coast of Central America.

Pectinnru is another large genus, distinguished from Oy</(//^/v/ by the absence of
the adhesion of the edges of the genital openings that, in the latter genus, doubles
their nundier. In OphioxoiKt the larger scales of the disc are intermingled with
lines of smaller ones, while OjiJiloca-itiiiia has none of these small scales, but is known
by large mouth-frames, developed into wing-like ]u-ojections, and by ;i vcrv loiiu- .and
large first arm-bone of \UHisual form. (>2>hio</li/itI,ii is a genus with fifty-eight known
species, all of which have numerous tentacle scales, while the j.air of tentacle ])ores
nearest the disc are slits of comjiaratively large size, sm-rouinled by numerous tentacle
scales, and opening diagomdly into the mouth slits.

In Ophlocteii the side arm-])lates are large, meeting belou the arm, but not above;
while in Ophlomusium l)oth u])[iei- and under arm-plates are so small that the side
arm-plates meet both above and lielow, while the radial shields and ])lates of the upper
surface of the disc are intimately soldered together, f<u-ming a surface like jjcn-celaiu.
O. JiuheUinn is a curious little form, with very short, rapidly tapering arms, and the
first pair of side arm-plates of each arm so large that thev nu-et in the inter-brachial

150

LOWER INVFAITEBRA TES.

Flu. 130

nlfata.

spaces, and thus seem to form part of the disc. Tt wns fdiiml off Port Jackson in
30 to a5 fathoms.

In all the foregoing genera, as well as in sc\ cral otlu'rs, the .■inn-sijines are

situated on the outer edges of the side arm-)ilates,
and are jiarallel to the arm, hut in the remaining
genera the spiiu's ai'e set on the si<les of the side
arm-plates, and stand out at a lai-ge angle with the
arm. The sjiines are thus mucli more eons|iieuous
than in the first gr<Hi]i, and in nian\' cases thev are
not t)nly long, hut adorned with j-ows of small, jiointed
teeth. In Opliiopholis the uji]ier arm-jdates are sur-
rounded by a row of siip)ilementar\ pieces, and the
lowest spine of the outer arm-joints is ;i hook. A
well-known s])eeies is O. aciileata, which is found at
various depths, u]i to 400 fathoms, on the coast of
northeastern America and northern Europe, as well
as in the Arctic seas. It is often called 0. hel/i,% hut was first described under the
name before given. . Ojjiiiactis, with twenty-four sjiecies, resembles the last genus,
but the upper arm-])lates are with-
out the ring of supi)lementary
pieces. In both genera tlie arm-
spines are stout and smooth. O.
savignyi ( O. vireKcexit) is fouiul
along the west coast of North
America, from Panama to Cape
St. Lucas.

A7»phi>ira is the largest genus
of the m'der, since it contains eighty-
nine known species, all of which
have a small and delicate disc, cov-
ered with over-la])ping scales and
showing the radial shields, and long,
slender, more or less flattened arms
with short spines of uniform size.
A. maxima, obtained by the Ch.al-
lenger expedition in 9° 59' S. lat.
and 139° 42' E. long., at a depth
of twenty-eight fathoms, measures
nearly a foot across from end to
end of arms, though the disc (uily
slightly exceeds half an inch in
diameter. Ophlovukla differs from
Amphiura prinei])ally in the jires-
ence of small spines upon the scales
of the disc. There are, in fat^t, sev-
eral genera that are distinguished
from Amphiura by but slight characters, though the differeiu'cs between the species
contained in those genera are curiously well marked and constant. Hemipholis

Fid. VM.— O/ihiir-tis Minijiii/i.

i^ERPENT :^TAIiS.

151

cordifera, a member of a oemis nearly related tn Aitijj/ikn-d, is ]ilentiful in the harbor
of Charleston, S. C., and is apiiarently vivi)iarous, since it may be found with minute
young elinginii; tn the amis and ilisc.
[t occurs also in the West Indies.

Op/docijmbiiun rarernonuiii, taUcii
l)vthe 'Challenger' east of Kerguclcn
Island, is remarkable for tlu' manlier
in which the clisc, which is scarcely
attached to the arms, ami is entirely
covered with small scales, overlies the
arms "like a Basque caji." (JjJiid-
roma iithiojjs and 0. ale.i-<niilri. are
large species from the west coast ot
North America, .\moiig the genera
with numerous long, usually rough <ir
thorny, arm spines the principal arc
Uphktcmttha with thirty-nine de-
scribed species, and Ophiothrij; with
tifty-six species. The species of
Ophiacantha can be readily distin-
guished from each other by points of
internal and external structure. Tlic

l.lii. — (tplihtcantha cili'hfif

spines vary from four to eleven in num-
ber at each arm joint. (Kvim2xini, ^^■hk■h
is widely spread in the southern ocean,
occurring at depths varying from 20 to ()0U
fathoms, carries its young, till they are quite
l.irge, in the ovarial bursa or ]iouch, whence
they often thrust an arm through the gen-
ital openiug. The bursa? are pleated bags
haviiit;' lime scales in their substance and
.•idhcring to the thickened wall of the diges-
tive cavity. Some of the basal arm spines
of Ojihioiin'tiri dijimcos dredged by the
•Challenger' off Culebra, West Indies, in
o90 fathoms, are from five to seven times
the length of the arm-joint. The species
of Ophiothrix are exceedingly ditticult to
distinguish from each other, although the
genus is well marked by the \-ery large
three-sided radial shields, disc set with
thorny grains; five to ten glassy spines
(beset with thorns, aiul often three times as
long as the joints), on eacli arm joint ; single,
small, spine-like tentacle scales on each arm-
joint ; swollen interbrachial spaces ; and
want of ]ierfect union between the halves
of each mouth-frame. The vertebne of the arms have a peculiar projection which in-
terlocks into a slot in the ]ireeeding bone, thus giving a fulcrum (says Lyman) for the

Fig. Kio. — Olikio(hn:v fratjilii^

152 LOWER IKVKllTEmiATES.

powerful musculMi- notion called for in the r:ijii<l whi])-like motion of the arm. O.
liiteata ooeur.s in Florida, and three or four 8j»ecies are found in southern an<l Lower
California. Ophiufkisina (ttttniKitiim is a curious form found in the South Atlantic.
The exam)iles taken had six arms, the disc is covered with thick soft skin, and the
arms, which are vei'v long and slender, have the lower and side jilates iin])erfectly
calcified, and no u]i]ier plates. The s])ines are short, three on each joint. The two
known sjiecies of Ophiohelus are remarkahle for the curious minute s])ines or jiedicel-
lai-iie, havins the form of a lonji-handled parasol, that take the i)lace of the true arm-
s]iines (ui the outer arm-joints. One of the most singular of ophiurans is Ophiothelia
suppUvans, iu which the disc is sha])ed like a high sugar-loaf, and the arms can l)e raised
u)iwards. The arms hear u])on all the joints beyond the ninth a cluster of three or
four minute ]iarasol-like jiediiellai-ia', set a little inside the true arm-spines, which con-
tinue to the end of the arm. The under surface of the disc is curiously ornamented.
A fiiil of long, flat, curved jiajiilhe is set upon each mouth-angle, which, ending in-
wardly in a sharp tooth, resemble so many birds' heads with ajtointed bill. Externally
to the mouth ]ia])illte are three ]iaralk'l rows of regular club-shajied flat jiapilla?. This
form is only known from south-west of Juan Fernandez, ami was taken at a depth of
one thousand eight hundred and tweiity-tive fathoms. Ophyminjces has a very jh'cu-
liar aiTangemeut of mouth ])apilla', and two of its sjiecies occur between five hundred
and <inc tlidusand fathoms.

Two or three genera of Ojihiurida' contain s|iecies with cylindrical arms, while the
entire animal is clothed with a thick skin, and the arm-])lates are imperfectly develojted.
Thev thus a]i|ir(iach the Astrophytida-. In Ophiobyrsa riulis. which was taken
off the entrance to Port Philip, in thirty-eight fatlioms, each arm is about twelve
inches long, though the disc nu^astu-es only about an inch.

Opihlonn/xa vivipara is, as the name im))lies, a \ivij)arous s))ecies.

The best known genus of A.sti!ophytu>,k is Astrophi/ton itself, of which seven
species are known. Though there are no arm-sjiines, the oiiter bi-anchcs of the arms
have s]iiue-like tentacle scales. The long bar-like radial shields of the disc are covered
by the thick skin, but show as elevated radiating ribs reaching to its centre. Under
the skin of the arms there are side arm-j)lates, which cover the lower side of the arms,
but there is onh a basal undi'r arm-jilate, and there are no u|i]ier arm-plates at all.
GorijoiairephuJiig has also branching arms, but the ]ilates under the skin of the disc
are differently arrange<l, an<l the arms, wide at their base in Astfopiii/tmi, are here
narrow, while the forkings are less nmnerous than in that genus. The young has at
first a flat disc covered with plates like that of an ordinary ophiuran, this first becomes
covered a close granulation ; then both the granulation and the disc-jdates atrophy,
exce])t those of the margin, which continue to grow and inulti]ily; and finally the
radial shields acipiirc their great length and height. In J'Jiiri/a/e no projier arm-s])incs
are ])reseiit, and in Astrodon and TrldiOKter the forks are but few. The total length
of an arm of T. pri>]m(/nutoris is about sixteen inches. Among the Astro]ihytida> with
unbranched arms the |)rinci|)a] uenus is Astror]n'>i(i(,^\\\w\\ has well-formed under arm-
plates like an o|ihiuran. Ojihioririix ulii/nsli'old was taken in twenty-three hundred
fathoms.

Order II. — ASTEROIDEA.

The differences which distinguish the star-fishes from the ojihiuroids are scarcely
less important than those which separate either from the sea-urchins, yet the external

STAH-Fl.'iHES.

15?

form is in both eases that of a star of live or more rays. In the star-fishes there is no
such well-marked distinction between the disc and the ai-nis as there is in an o]jhiu-
roid, for the stomach, and the ovaries or sitermaries, nui into tlie arms. Along
the underside of each arm runs a deep ambulacral furrow, from the de]iths of which
project the ambulacral feet, which are j)rovided at their ends witli stu'kers, by means
of which the •■uiimal moves. At the base of each sucker-foot within the ana is a
vesicle or amjjulla, connected with the radial or ambulacral canal of the water system.
This arrangement seems very different fi'om the solidly ])!ated arm of a serpent-star,
with its enclosed row of vertebral o.ssides, and its tentacle-like feet uu)ir(i\ ided with
sucking discs or with vesicles at tlieir base, yet it is demonstr.-iblc that the halves of
the vertebne of an <i]ihiuran are to be considered identical in tlieir nature with the
calcareous ambulacral pieces which form the dee])er ])arts of the sides of the ambula-
cral furrows of a star-tish. The develojiment of the interambulacral areas varies
greatly, so that while some star-fishes, as Brlsiiii/a, closely ajijiroach the serpent-stars
in the distinctness of the arms, others have the angles between the arms more or less
tilled up liy the development of the interambulacra, which in many forms are so exten-
sive that the creature is nearly or (piite a pentagon, and the existence of arms can onlv
be traced by the lines of the amliulacral furrows on the oral asjiect.

Star-fishes have a very complex skeleton, varying greatly in the different groups,
Init always consisting of plates or thick rc^ds composed of a dense calcareous net-work.
The sides of the ambulacral furrows are bounded by two rows of regularl\-]ilaced and
similar amltulacral ossicles, which alnit against each other like the two sides of a gable,
while at their outer ends they al»nt against a row of short, thick, adaml)ulaci-al or
hiteraml)ulacral ossicles, which form the borders iif the furrow. These are the
constant parts of the skeleton, but the sides of the arms are in many cases enclosed by
plates of considerable size, known as margimd jilates. The net-work of rods which
forms the support of the n])])er ]iart nf the arms and disc is very variouslv developed
in the different families and genera. The pores through which the sucker-feet ])ass
are each formed by two amliulacral ])lates, one half of the pore consisting of a ncitcli
up<jn the outej- side of one ])late, while the other half is on the iimer side of the next
]ilate. .Vround the mouth the ambulacnd and interambulacral ])lates are modi-
fied SI) as to form a ]ientagon or polygim. The jiieces of this calcareous ring that cor-
respond to the interaml)ulacr.-d plates of the arms are furnished with strong jiapilhe or
spines which form a sort of im|)erfect dentary ap|)ai-atus. The s]iines wliich jiroject
from the surface, both above and lielow, .and which usuallv fcirm regidar
rows on each side of the .ambulacral furrows, are more or less movably
united with the skeleton, but are without the regidar joints found in
the sea-urchins. Pedicellariie are ]n-esent. Above, that is to s.ay, in-
ternal to the dentary jiajiilhe, the gullet opens into a wide stomach,
the oral or cardiac part of which is ]iroduced into sacs that sometimes
extend into the cavity of the arm to wliich they correspond. On the
.■iboral side of these sacs, the alimentary canal again narrows somewhat,
and widens again into a pyloric sac, the angles of which are ag.ain ]iro-
longed into tubes which run along the aboral side of the rays. The
upper or pyloric part of the stomach is attached by a mesenteric mem-
brane to the aboral wall of the body, while the cardiac sacs are similarly
connected with the ossicles or calcareous ])lates arouml the mouth. Beyond the ]iylorfc
sac is a short tubuhir intestine, which ends in a more or less minute anal pore, apparently

Vui. \?A. — SpiliP
•If st:ii--tish.witli
jiedii'Hllai-i.i :U
tlif luise.

164

LVWKH 1NVKI!ri:i;UA TES.

nidimc'iitaiT. Into the intestine (ij)ens ;i duct whieli divides in two main branches. These
liianclies subdivide into numerous tV)llicles, tlie whole forming what is suj)])Osed to be the
li\er, since it contains a bitter fluid like bile. The nervous system consists of a ner\e
which runs, as a longitudinal ridge, along each amliiilacral groove, and of a ring around
the mouth. At the end of each arm a rudimentary eye, continuous with the ambulacral
nerve, is placed at the end of a modified tentacle. The water system consists of a
canal running the entire length of each arm. This canal is placed in the angle foimed
by the ambulacral plates, and is thus external to them. It is sejiarated by a strong
partition from a second canal which intervenes between it and tlu' nervous band which
forms the bottom of the amlmlacral groove in the living ;mimal. Tliis lower canal,

Fig. 13.0. — Bipiiiii;iri:i of star-fish ; am^ rudimeulary
ambulacra ; i, intestine; o, anus; o3, cesopliagus; s,
stomacli; tr, water tubes.

Fig. 130. — Later larva, witli star-tisli fonniug ; m,
mouth: ab, abora! portion of star-tisb.

which is itself divided into two halves, is called the ambulacral neural canal, and com-
municates with a circular canal around the mouth. From op]iosite sides of the
ambulacral canal of the water system, short branches pass u]) between the ambulacral
ossicles to the ampullaB, which are sacs with muscular walls lying above the ambulacral
plates, and within the cavity of the arm. Each am]wlla communicates with a pedicel
or sucker by the i)ores in the ambulacral plates, as before described. The cavity of the
body and rays is filled with a watery fluid containing corpuscles, evidently represent-
ing the blood of higher animals. Pores, by which water can enter the body cavity,
are often present u)>on the aboral as])ect of a star-fish.

The se.\es are distinct, l)ut can only be distinguished by a microscopic examination
of the glands, which are situated on each side of the interior of the arms, or at the
juuction of the body with the rays. As the plates which enclose the base of the arms

STAR-FISHES.

155

in the long-armeil star-fishes arc interradial, and are homologous with those which fill
up the .sj)aoe between the arms in the pentagonal species, the ovaries are actually
interradial or interambulaeral in position, as in ophiuroids. The eggs pass out by a
]iore on eaeh side of the base of the arms, situati'd between two plates, and dittieult to
detect.

The embryo nf a star-fish is \isuaily a free-swimming animal with ai'ins and ciliated
bands, and has been called a Biachiolaria, or, in other forms, Bijiinnaria. The
Brachiolaria, when it has attained its full development, has thirteen arms — a medial
anal pair, a dorsal anal pair, a ventral anal ]iair, a dorsal oral ]iair, a ventral oral pair,
an odd anterior arm, Ijcaring an odd brachiolar arm, and a pair of smaller brachiolar
arms connected with the oral ventral ])air of arms. The br.achiolar arms have wart-
like appendages at the tip, whereas all the other arms are surrounded by chords of
vibratile cilia. The median .anal arms ajijiear first and are largest (in Asteracuuthioii
pdlUdus), and the odd brachiolar arm ]irecedes the jiair of similar arms. The adult
larvfe move about rapidly by means of the cilia, with the oral extremity in advance.
In the Bipiniiaria llie arms are fewer in nnndicr .■nid are moi-c slender, and all are
ciliated.

The first commencement of the growth of the young star-fish is by the appearance,
on the anal side of the left water-tube of the larva, of five slight folds; while on the
other side of the anal ex-
tremity aj)])ear five lime-
stone rods. The folds are
the first rudiments of the
rows of suckers, the rods
of the abor.al skeleton.
The rajs are indicated as
lobes upon the growing
dorsal ])art f)f the disc
while the suckers are still
widely separated from
them. The yoinig star-
fish, thus growing on the
opposite surfaces of the
two water-tubes, soon
loads down the anal end
of the embryo, the larva
then becomes sluggish, the
body changes from trans-
])arent to cloudy and
opaque, the arms contract
and become constricted
intci t'clls, .-md soon noth-
ing remains but the brach-
iolar arms, brought close
to the young star-fish V)y the shrinkage of the boily. These finally follow the rest.
Not a single part is (b-opjjed off, the whole of the larva passes into the star-fish. The
first steps sulisequent to this resorjition are the approach of the oral and alwral sides
by the contraction of the water-tuljes, and the approach to symmetry of the at first

Flc. 137. — ni:il siiifM

iif viTv youMK star-fish.

156 LOWER INVERTEHRATES.

unsymmetrical arms. From this strtge the arms orailiially lengthen, ami the spines
and sm-kers develop and increase in number until the adult form is reached.

In some star-tishes the emliryo devel<i]is directly witlmut jjassinLT through a free-
swimmino' stage, and this is especi.-iUy the case with species nf the southern seas.

Fro. 1;;^- ~ i:i^^hi<iu rarnnata.

Various adaptations of the spines and external mend)ranc form marsuiJia for the
protection of the young while attached Id tlu' jjarent. A large species of ^simas,
dredged in Stanley Harlwr, formeil a shelter for its young by drawing its arms
inwards and forwards over the month.- EchinuMvr sarsii does the same.

STAn-FlSHES. 157

The family Brisixcjid.e iucluilfs only two known spt'cit's, both iiihnbitants of deuj)
water, where they have an exceedingly wide distribution. Tlic genus ajij)r(»aehes
fi/ciiopodia and ('ronaa-sti'i; but in apiiearance is intermediate between the ophiurids
and the star-tishes, since it has a distinctly circumscribed disc like the former,
thouu'li the long arms are soft as in the latter. liritiiKja, rii(7i;f(irin;iiios has eleven
arms, which are nearly smooth, while the nine to thirteen .arms of II. coroimta have
transverse crests of s)iines. The .arms are sometimes a foot long, they are narrow at
their insertion into tlu' disc, cnlargi' (•onsi(h'rably towards the mi(hlle, where the
ovaries are develojicd, and tajicr thcnct' to the tiji. ]}. roronatd li.as a single genera-
tive organ, with a single o])ening, on each side of each arm, while li. eiiikraaietnoii
ha.s a great number of separate small <n-gans, each with its own opening, in a similar
position. The water-feet ai-e furnishrd with sucking-discs. IJows of long s|iines
covered with soft skin bor<ler the .■inibni.acral grooves; this skin is full of small
]icdicellaria', and groups of jiedicellari.e arc scattered over arms ami disc. The
creature is extremely fragile, and always breaks to ]iieces before it can be handled.

The Ptkkastekid.e are furnished with groups of di\erging spines, on the tips
of which a membrane is carried. Jli/n/tnaater p<illiiriiJti.<. was h'rst dredged in five
htuidred fathoms off the north of Scotland, and it has since been found that, with
perhaps the exception of Avchastet\ Ili/menuiiter is the most widely distributed genus
of deep-water asterids, varying from four hundrecl to t\V(] tlumsand ti\-c hundred
fath(uns.

JIi/)ii( mister iiiihilis is i-athcr :i large stai'-lisli, tiai inches .-icross. The five arms,
each two inidics wide, .ai-e united to each other by a bro.ad web attached to the (Uiter
row of the spines which fringe the ambulacral groove, thus transforminii' the animal
into :i large pent.agon. The entire up|ier surface, the web exeejited, is set with
bunches of four to six diverging spines .about an eighth of an inch long. These sjiincs
support, clear of the surface of the disc, a tolerably strong meml>rane, like the canvas
of a tent. Something similar to this occurs in Ptin-<iMa\ In the centre of the back
this arrangement is modified to form a brood ]iouch for the ^■oun^■. From five
calcareous supports, arising from the .amlinlacral jilates below, s])rino- a double series
ot spines, the outer series of three or fom- diverging in the ordinary wav beneath the
tent cover, while the inner series of six or eight iiend inwards, and have a special
membrane stretched between them in such a way that each series forms .a fandike
vahe, the spines closing wdien the valve is closed and separating when it is ojiened.
In this central pouch the young ai-c^ carried. This sjiecies was taken in eiii'liteen
hundred fathoms, about eleviai hundred miles southwest of Cajie Otway, Australia.

Korethruster hispidus was dredged near the Shetland Isles. It is a small star-tish
with the whole of its upper surface covered with long .spines (paxilla?) like sable
brushes, masking its true outline. Uows of delicate, spoon-shaped spines border the
ambulacral grooves. Another species of this genus, lu 2^(ilmat!es, has been dredged
in the Caribbean Sea.

rtf-nhster is the priucijial genus of this essentially deep-water family. In /'.
uniltlpes, of the Norwegian seas, there are four rows of water-feet, as in Asti;r!<is.

The AsTKoPECTixiD.E'are forms with long niys ending in a ])oint, thus rescmhlinir
in general shajie the Asterid:e, from which they differ in having two rows of ambula-
cral tentacles, which are usually without sucking discs at their extremity, and also in
the character of the skeleton, whicdi is forme<l, at least in the dorsal region, of con-
tiguous ossicles, often shaped like an hour-ghiss, and bearing tubercles which are

158 LOWER INVERTEBRATES.

crowiu'il witli small tufted spines called ])a.\illi. They are most numeious in the hot
seas.

The genus Astropecten is a large one, and many species occur in deep water. A.
articidatus ranges from New Jersey to the West Indies. Several sj)ecies are known
to occur on the west coast of North America.

Nearly allied to Astro-pecteu, hut differing from it in the very conspicuous feature
of the ahsence of any large marginal plates on the sides of the rays, is Luidiu, the
brittle star-fish, celebrated for its power of breaking intu fragments when it is brought
from the bottom. L. duthrata ranges from New Jersey to the West Indies, and is
common in the C'arolinas. L. tessellata, a fine .species, attaining a diameter of more
than a foot, ranges from the (tuU' of California to Peru. Vtenodiscus criqKttus is
another North Atlantic species, occurring in the North Sea, Greenland, and New Eng-
land. It is almost jientagonal from the shortness of the rays.

L>>pUjr} Ulster kertiuelenensis has its dorsal surface covered with a tessellated pave-
ment of ]iaxilli or sjiines, with large heads. These paxilli form with their aj)proxi-
mated heads a sort of hexagonal mosaic on the surface, but between their slender
shafts arca<le-like spaces are left, and into these spaces the eggs pass from the genital
openings. Eggs and young in all the early stages of development occupy these spaces
at once, hut when at least six suckers have foruu'd <iii each arm, tliey push their way
out between the paxilli, usually iu the angles l)et\\eeii the arms. The young escape
mouth u])permost, and disengagi' their arms (iiie by ciuc. After this they remain at-
tached to the jjarent for some time, iu tlu' young, thc> mudreporic plate can lie seen
near the margin of the disc, but in the adult it is hidden by the ]iaxilli.

A)'chaster vexilUfer, taken in tliiee hundred and forty-four fathoms, west of the
Shetland Isles, is a fine species about ten inches across, remarkable for the arrange-
ment of the ambulaeral spines, which form coniKs that increase in size toward the
base of the arms. Each ]ilate has a double i-ou of s|iines. .and each s|)ine has a
second short s]iine at its end. 'i'he anibulacr.il grooves are much widei-, and the
ambulacra! tubes larger in jiroportion to the animal than is ustuil.

Arcliaxtcr bifrons, taken in <lee)i water north of the Hebrides, measures five inches
across, and is of a rich cream or light rose tint.

PorrellatHister rwridens was dredged by the 'Challenger' in one thousand two
hundred and forty fathoms, in the Gulf Stream. The arms are rather shortei- than the
diameter of the disc; the ambulacra! ])lates are large, and furnished with two tlat-
tened spines; and the plates forming the angles of the mouth are unusually flattened
and expanded. There are two rows of large marginal plates, and the two on the end
of each arm are fused together, and bear three spines, one on each side below, and a
central one .above. Vertical rows of small flattened scales cover the two central
pairs of marginal ]ilates in the re-entering angles between the arms, and look like a
little brush between each pair of .arms. The njiper surface is covered with narrow
calcareous jilates, and is of a rlelicate cobalt lilue color. The excretory opening is
verv distinct in the centre of the disc. Jt has been found in the North Pacific and
near Tristan d'Acunha.

The AsTERixiD.E are pentagonal, more or less elevated in the centre of the disk.
and always sharp at the edge. Spines are present, at least on tlie ^ entral stirface, and
there are two rows of pedicels in the ambulaeral grooves.

Asteropsis imbricata,a species which ranges from Yancou\ er's Island to near San
Francisco, is a good example of this family. The skeleton of the abor.al side is a retic-

STAR-FISHES. 159

Illation of fl.it, irrescular, star-sh;\|ic(l jilati's. from which diverge loiifjer flat pieces
connecting the others tom'ther: the plates and tlu'ir connecting links are all imbri-
cated, that is, overlaji each either.

Asten'/ia foliioii occurs in the West Indies and in Floriila. Asteriiia is a large
genus, almost world-wide in its distribution. The skeleton is formed of imbricated
or over-lai)}iing .-nid notched ossicul.-i, and this structure is usual in the family, an ex-
ceiition beiui;' IHadsttriini <i///ioriii(ih's, in which singular sj>ecies, a native of tlie coast
of New Caledonia, the plates oi the back are disjoine(l, leaving between them mem-
branous spaces, most of which are piei'ced by a tentacle. In the genus Patiria, the
plates of the b;ick .ai-e i-ounded, and simply touch each otlici'. /'. cntgsii is from
Western .\ustrali.-i.

In the ( JoMASTKKiii.K, (he skeleton, at least on the lower I'.-ice, is foi-nicil nf rounded
or polygonal ossicles, forming a kind of pavement, and there ai-e usu.ally two rcjws of
marginal plates of comjiaratively large siw. Tlu' body ajijird.iches more or less to the
pentaiional sha])c, the arms )irojecting but slightly, and there are two rows of suckers.
Some very tine ex.iniples of this family are fotuid ii]ion the west coast of this con-
tinent. Froniineut .among them is Oreaster occidental is, which measures eight or
nine inches across, and is also of consi(hM':iblc thickness in the centre of the disc. It
ranges northward Xo Lower t'alit\)rnia.

A very licautiful .sjiecii's, with long, sharp spine.-- upon :i liright red disc, is Nido-
rellia ttnniifa, a pentagon.-il, c.'ike-like star some tive or six inches across. Afnp/riaster
insii/niii, another Lower C-difornian species, has short, flat arms and a flat disc, and the
regular an-angement of its spines and tesselateil plates reiulers it exceedingly beautiful.
A more northern species is AFcdiuster m/au/i^. which has been found as far north as
Puget Souiiil.

Antrof/oiiium phri/i/!<iiiiiiii. is ;i large, bright-red pentai^dual st.-ir-tish, whit'h resides
at de])ths of from twenty to fifty fathoms, on rocky bottoms, in tlu' C4nlf of M.aine and
northward. A. iinmulara is from Scandinavia. Pi'iitncerofi retlctdutKK is about eight
inches across the arms, and is found on both sides of the Atlantic, at the Gape Verde
Lslands, and in the West Indies. In Cidcita the shape is pentagonal, and the ti]is of
the ambulacra appear on the dorsal surface. The (Toniasteriihv are more numerous
in types than any other family of star-tishes. Their ]irincipal centre of distribution
seems to V)e the west coast of Austndia and the Malaysian and Mclanesian archi-
pelagos.

The LixcKIAD.E li;i\'e :\ skeleton enniposeil cif ivniiided or elliptical ossicles, either
contiguous (ir united by rods. There are no spines, but the surface of the body is
smooth or uniformly granular. The species arc most numerous in hot reiiions.

JJiickid H/ii/UsriaHs, a tiiu' species ranging from Lower California to Peru, and
Linrkiu (juildiiKjii, i.)i the West Indies and Florida, are examjiles of the typical
genus. OpMdiaster jii/riniild<dis is a large species with the s.-mie range as L. t/ni-

J'lisriidin.

The Kiiiix.vsTKiiiii.i:, as detineil by Perriei', liax'e ,a skeleton comjioseil of a network
of lengthened ossii'les, .-md have two rows <if ambulacral feet. Spines arise from the
ossicles of the <lorsal surf.ace.

Echinaster aentus is .-i flve-armed species, alnnidant in the West Indies and
Florida, and extending udvth to Xew Jersey. The s]iines are completely sheathed in
membrane, and occur oidy at the .-mgles of the limestone |)olygons of the dorsal
surface. tSolaster endecahns eleven or fewer smooth arms, and is widely spread in the

IrtO LOWER INVERTEiniATES.

North Atlantic. Its j)laL-u in thu North Pacitic is taken by S. dcceinrudluta. Thu retic-
ulation of the skeleton is close, and the arms less flattened than in the next sjiecies.

Crossastcr 2X(piJ0sus is common to Ijoth sides of the Atlantic, and is found in Nor-
way, Denmark, Britain, France, and in America as far south as Massachusetts Bay.
It has twelve aims, the spaces lictween which are largely filled up ujion the oral side
1)V a memhrane, while the u]>)ier surface is an o]ien network of limestone rods, carrying,
at the points of junction, cluh-sliaped ]irocesses which bear t\d'ts of small siiines.

Cvibrelhi s<;v-r(iili<it<:(, from tjic Antilles, is rem,irkal)le troni its possession of six
arms, an e.\ci')>tional character in this genus. It has also the faculty of reproduction
by division into two halves, so tliat most examples show three larger ami three smaller
arms. Tjiis power is also possessed by se\eral of the man\-.'irme(l , /^■^.'/•/"*', by some
/Jnckias, and some Asterlnns. CrlbrMa ^uiujuiiKilcnta is common on the New
England coast below low-water m.irk.

The ,VsTEi;iii.io arc star-tishcs which usually have the arms well-develo]ieil, and have

four rows of water-feet, each ending in a
sucking-disc, along the ambulacra. One
of the largest genera is Aster ias, or Astcr-
iiriiiitJiion, sjiecies of which are found
everywhere in the northern hemisphere.
A. ri(/)eiif is ;\ comnu)n European form.
.1. l>ci\i/linut< extends from Halifax, Nova
Scotia, to Floricl.-i, while A. vif/f/itris
langes from Long Island Sound to Lab-
i-adin-. The l.-ist two species are bolli
(■(innnon in Jlassachusctls Bay.
-^,„,. ■. -.."^vi-. In A. orhrucea., which ranires from

Is'" \' Xw?-. Sitka to San Dieu'o, and is the most com-

'I'-n.--

/^^0^ \''W% nion star-fish of the ('•■iliforui.-in coasi, the

^i-K'M''' \i-'x$., arms .and the ambulacra are wider than

^&' fe;^)^ in most species of the genus, and the cal-

^^' careens network wliit'li covers in the sides

and l)ack ot the arms is exceedingly solid.
Several other s])ccies of J.v/r/vV^s- occur ujiou the Pacific coast of the United States,
but the most conspicuous is the large six-armed .1. t/i;/i(iifr<>, which attains a diameter
of more than two feet. Nearly allied is Fi/r)n,po(Ua heHiintlniiik.% a gigantic form
with more th.an twenty arms, common on the P.-icific coast of North America, from
Cajie Mendocino to Alaska; the calcareous skeleton of the njipcr surface is reduced to
a few small rods at the l)ase of the s] lines, and hence a large well-iirescrved specimen
is a rarity. Tiiis species attains the diameter of three feet, or thereabouts, and is of
.1 bright red color in life. Professor A. Agassiz considers th.at this sjiecies, as well as
Crossaster /Dipposi/s, are in many resjieets allied to Bris!i);/ii.

The many-armed Asterid:e are, for the most jiart, included in the genus JhJinMo;
or sun-star, two species of which, // /n/biinj'' and II. ndcrobrachia, occur ujion the
west coast of North America, from Panama to C'ajic St. Lucas. The latter form has
more than thirty arms, and the free portions of the arms are very short.

Zoroaster ful(/en«, dredged northwest of the Hebrides, has immensely long arms
and a very small disc, not one-twelfth of the total diameter of the animal, which
measures ten inches across. It closely resembles Op/rkh'aster, but luis four rows of

starfish, Holotliurian. and Worms.

SEA-URCHINS. 161

watei'-feet in the nmlnilncral grooves. Zoroaster aigsheei and Z. orkleyi are two
species dredged by the 'Blake' in or near the Caribbean Seas, in 1878-79. The last
attains a diameter of about nine inches across the arms. Though the suckers are
ranged in four rows at the base of the arms, there are but two rows at the extremity.
It greatly resembles an Ophidiaste.r in general appearance.

The small size of the sucking-discs of the water-feet, and the general aspect of the
animals, suggest that the genus should be placed witli the Astropectinidag, near to
Luidia.

Caulaster is a singular star-fish, furnished with a peduncle in the centre of the disc,
suggestive of tlie centi'o-dorsal tubercle of a comatula. It was taken by the French
exploring expedition.

Class III. — ECHmOIDE A.

The Sea-Urchins are echinoderms without arms and without a stalk. They are
protected externally by a calcareous test, composed of plates known as the coronal
plates. These plates form ten distinct areas, five of which are perforated with pores
for the exit of the suckers, and are known as the ambulacra! areas, while the five
intermediate areas bear no suckers, and are known as interambulacral. The variations
in the form and size of these plates, and of the areas they compose, give rise to the
varying shapes of the different genera. The mouth is always situated ujion the lower
or actinal aspect, which is applied in progression to the surface upon which the animal
moves ; but the position of the anus vai'ies in different families. The surface of the
plates, except where the pores are situated, is covered with spines, which occur upon
every species of echinoid, but vary greatly in their number, structure, and size, so
that they form one of the best characters by which species can be distinguished.
There seems at first sight to be little resemblance between the huge bat-like spines
of Heterocentrotus, the sharp, hollow, brittle spines of the Diadematidre, the solid-
fluted spines of the Echinidie, and the slender, delicate spines, usually short, but
sometimes long and silky, of the spatangoids or irregular sea-urchins, yet A. Agassiz
assures us that in their early stages the young spines of Echinids are much alike.
They are polygonal, made \\\^ of rectangular meshes placed in regular stories one above
the other. There is no difference in the typical structure of the spine of the young of
Cidaris, Echinus, Strongylocentrotus, Arhacia, ErJii- ^<^^;:zzt~~^^^>^

nocyamtis, or Schizaster. Some recent genera, espe- X^^^^S^^^X^

cially the spatangoids, retain a type approaching X/ ')'y^^^t\/\K^
that of all young echini, while among many oldei' //// (/\ fl 1Vn\\\\\\
genera, as in Cidaris and other regular sea-urchins, /th|v!''''"«~x* , .-^■""'^^iTHm
complicated types occur. [I ]li-\ Hto».^^4-«iM«'^ p^^

The coronal plates are more or less pentagonal, VX \^^~^£j^^ '\jlr-Ll I
and are usually firmly united at their edges. Twenty V ^ T^v^"4c/// — '

principal longitudinal series, two in each ambulacral, ^e.'^ ^^^%%^y

and two in each interambulacral area, make up the v,.^ ""I^^^^^^

mass of the test, and a series or rosette of ten single XjJl.^&^^S^^'^

plates form a ring round the aboral or apical margin, fig. 14o. - Erh,naraA:imms parma ,• a. am-
The apical extremities of the ambulacra abut upon ''"'*"^'' '■ inf^-ambuiaorai areas.
the five smaller of these plates, each of which is perforated, supports the eye-
spot, and is called the ocular plate. The apical ends of the inter-ambulacra cor-

VOL. I. — 11

162 LOWER INVERTEBRATES.

resj^ond to the five larger jilates, which are perforated with a larger aperture for
the escape of the generative products, and are called genital plates. One of these
genital plates, lying in what is recognizable as the right anterior inter-ambulacrum,
is larger than the others, and has a porous, convex surface. This is the madre-
poric body, and communicates with the water-system. Within the circle formed
by the genital and ocular plates are a number of small plates, of which one, the anal,
is larger than the others. The anus lies slightly out of the centre, between the anal
plate and the ])OSterior margin of the anal area. The space around the mouth
(peristome) is usually strengthened for some distance by irregular oral jilatcs; and
ten rounded plates, supporting as many suckers, and perft)rate(l by their canals, are
placed in jiairs close to the lip.

Each of the double series of coronal plates presents a zigzag suture
in the middle line. Each ambulacral plate is subdivided by a greater
or less series of sutures into a number of smaller jilates, which are per-
forated by the pores of the suckers, and are called pore-plates. These
are the ju-imitive ambulacral plates, and in tlie Cidarida? do not coalesce
into larger ambulacral jilates, but sim])ly enlarge.

Scattered over the body, especially near the mouth, ai"e the pi-onged
pcdicellarire ; and on most living echini, Cidaris excepted, small button-
like bodies called siiha?ridia are found. These are situated upon a short
stalk, and are thought to be possililv organs of taste. The spines or
other appendages of the test are mounted upon tubercles, the size of
which is proportioned to that of the spines, so that the empty and

Fio. 141. - Pecli- '

ceUariaofsea- denuded test of a sea-urchin, covered with poi'cs and tubercles, tells
much respecting the affinities of its former habitant.

In a large portion of the class, the regular urchins and the cake-urrhins, the mouth
is furnished with five pyramids or jaws moved by powerful muscles, and in the regular
sea-urchins each pyramid is composed of eight pieces, making a total of forty pieces.
The digestive canal consists of a narrow gullet, a stomach of considerable length,
passing from left to right around the interior of the body, and then turning uji and
curving back in the opposite direction ; and of a terminal intestine. The stomach
forms two series of loops, partly enclosing the ovaries, and is held in ]>lace by a broad,
thin membrane, the mesentery. The sexes are distinct, and there are five ovaries or
spermaries, opening outward by the openings in the genital jilates. The single madi'e-
poric canal extends from the madreporic i>late to the eii-cular vessel around the
mouth.

The majority of the Echinoidea undergo a metamorphosis, the early stages of which
are similar to those of the star-fish. The embryo sea-urchin is called a pluteus, and is
furnished with eight long amis supported by slender calcareous rods. These arms
and rods are the locomotive apparatus of the young animal, which jn-ogresses by open-
ing and closing them like an umbrella. The body is also provided with a curiously-
curved band of vibratile cilia. Anything more unlike a sea-urchin than one of these
plutei, with its complex sprawling array of arras and bilaterally spnmetrical, but not
radiated body, cannot well be imagined.

In Stronf/ylocentrotus drobachiensis, the common urchin of the Atlantic coast, the
rudiments of the first tentacles appear in twenty-three days, by which time the pluteus
has acquired its com]ilete external form, but the shajie of the larval digestive cavity is
concealed by the growing sea-urchin within. The body of the pluteus is gradually

SEA-URCHINS.

163

absorbed, and the spines and suckers of the young sea-urchin increase in size and num-
ber. When the phiteus has finally disappeared, the young sea-urchin is more like the
adult than is the young star-fish, but the plates of the apical region are not only more
conspicuous in relation to the size of the test, but differ somewhat in their arrange-
ment from those of the adult. The anus is at first wanting, and the anal plate is rela-
tively large, is in the centre of the ajiical area, and is united by its edges with the five
plates which, though imperforate in the young, become the genital plates in the adtdt.
The other five plates that surround the apical system (the ocular plates) are also im-
perforate, and from a circle outside that formed by the genital plates, the spaces
between them being occui)ied by interambulacral plates. In this stage the homology

Fl.G. 142. — Old pluteus of Arbacia, with developing sea-urchin.

between the apical region of a sea-urchin, and the calyx of a crinoid is strongly brought
out ; the anal plate representing the basalia, the genital jjlates the parabasalia, and the
ocular plates the first radials. The ambulacra may therefore be taken to represent the
arms of a crinoid, and the interamliulacral plates of the echinids are homologous with
the interradial plates of the Crinoidea. The calcareous skeleton of the pluteus under-
goes resorption, but the remainder of the larva passes into the growing sea-urchin.

The pluteus form is not universal among echinoids, since several forms from
the southern hemisphere {Ilemiaster pMlippii., H. cavernosics, Anochamis sinensis,
Cidaris nutrix, etc.), develop directly into sea-urchins without, or with only traces of,
a metamorphosis. Notwithstanding this great difference in the mode of development,
the species which develop directly are very nearly related to species which live in the
northern seas and pass through the pluteus stage. The ' Challenger ' expedition did

164

LOWER INVERTEBRATES.

not find any free-swimming ecliinoderm larvae in the southern ocean. In tlie species
which develop directly, some of the plates and sijines are modified so as to afford

protection to the ova and em-
bryos, which remain attached
to the i)arent during the early
stages of growth.

Most of the regular sea-
urchins affect rocky coasts,
and many of them, by what
agency is not known, burrow
into limestone rocks and coral
reefs until they lie in a cavity
which fits their bodies.

The total number of genera
of Echinoidea known is not
more than two hundred and
twenty-five, represented by
about two thousand fossil, and
less than three hundred recent
species.

Twenty-four gene r a o f
echini now living, including several spatangoid forms, were already existing at the
time of the earliest tertiary formations, and some of these date back to the Jurassic
beds, or even to the lias and trias. In tertiary times occur thirty-eight additional
genera which have come down to the present time. The tertiary fossil echinids of the
European beds are so similar to those now living in the West Indies, that it is nearly
impossible to distinguish the species.

The southern ocean is the home of most of the deep sea or aliyssal species, some
fifty in all, and only one of these, Poiirtalesia pMale, extends into Europe in deep
water, though a comparatively large number of PourtalesicB and Echinothuridas extend
into the North Pacific. Twelve of the abyssal sjiecies extend beyond two thousand
fathoms. Forty-six species maybe called continental, occupying an intermediate posi-
tion between the littoral species and the abyssal forms. Ten of these species extend to
great dejaths.

The orders of the Echinoidea adopted by A. Agassiz in his report upon the residts
of the 'Challenger' expedition are the Palfeoechinoidea (extinct), the Desmosticha
or regular sea-urchins, the Clypeastridce or cake-urchins, and the Petalosticha or
irregular sea-urchins.

Fir,. 143. — Young of Strontjyloccntrotus.

Order I. — DESMOSTICHA.

This order includes those sea-rirchins which have a perfectly regular form, the ambu-
lacra commencing at the aperture of the mouth and continuing around the test, which
is more or less globose, until they reach the apical system in the centre of the upper
aspect of the test. The mouth and anus are thus in this order always to be found
upon opposite aspects, the ambulacra divide the circle of the test at five equal
angles, and, excc])t in a very few instances (in the Eehinometrid.a?) there is no dif-
ference in length between the two equatorial diameters of the body.

SEA-URCHINS. 165

All these regular sea-uicLiiis, as they are commonly called, have a highly complex
mouth apparatus. Each of the live pyramids consists of a hollow, wedge-shaped
alveolus, composed of four pieces, or rather of two lateral halves, each formed of a
superior and inferior portion ; and of a long, slender tooth, shaped somewhat like the
incisor of a rat or other rodent. The live alveoli, with their teeth, form a cone, and
the parts are united together by strong transverse muscular fibres and also by long
pieces applied radially to their upper edges. These radial rods are the rotulaj. To
the inner end of each rotula is articulated a slender arcuated
rod, with a free forked extremity. These are the radii. Thus
the entire apparatus, usually called ' Aristotle's lantern,' consists
of twenty principal parts, five teeth, five alveoli, five radii, and
five rotula;, and as each alveolus consists of four, and each radius
of two parts, the total number of pieces is forty. When in
position, the alveoli and the teeth face the interambulacra, the
radii and rotulae the ambulacra. For the attachment of this
dentary apparatus to the test, the coronal plates of the margin
of the mouth are produced into five perpendicular perforated
processes, calleil the auricles. These usually arch over the am-
bulacra. From the auricles and interambulacra! spaces at the fig. »4.- Aristotle's lau-

^ teru of Arbacia.

margin of the mouth arise a complex system of muscles, jiro-

tractor, retractor, and oblique, inserted into various parts of the mouth apparatus, at

once attaching it firmly anil regulating the movements of the parts.

There is great variation in the size, shape, and surface of the spines of the Desmos-
ticha, but they are never so delicate and silky as in the other orders of echinoids.
Usually certain large spines which form a continuous series from one end of an intei'-
ambulacrum or ambulacrum to the other may be distinguished'as primary spines, while
the smaller spines forming less complete series are known as secondary or tertiary.
The tubercles to which these spines are movably attached are in some cases marked
by a central pit, into which, and into a corresponding pit on the head of the spine, a
ligament of attachment is inserted.

The radial ambulacral vessels reach the ambulacra from the circular canal around
the mouth by passing beneath the rotulas and through the arches of the auricles.
There are large ambulacral vesicles at the bases of the suckers, which are usually ex-
panded into a sucking disc at their tips, where they are strengthened by a calcareous
plate ; but in some genera the j)edicels of the apical part of the test are flattened,
pectinated, and gill-like.

The family Cidaeid^ has a large number of small plates in the ambulacral areas,
and the pores are arranged in single pairs. The iiiterambulacral regions are very
wide, with only a small number of tubercles, each of which is large and perforated,
and bears a massive solid spine. There are no secondary spines, but the entire surface
of the test between the primary spines is filled in with small papilla', which extend
also over the oral membrane. The areas occupied by the oral and anal systems are
larger than in other regular sea-urchins ; the jaws are less complicated than in the
EchinidoB and Diadcmatida?, the teeth are gauge-shaped, and the auricles are inserted
in tlie interambulacral instead of the ambulacral areas. Processes developed from the
ambulacral plates form a sort of wall on each side of the ambulacral canal. The
ambulacral plates are continued on the peristome to the margin of the mouth, where
their edges overlap, producing a structure somewhat like that of the entire test of the

160

LO WER IN VER TEBRA TES.

Ecliinothuridae. Cidaris metularia occurs in the Pacific and East India oceans, C.
thouarsii on the west coast of North America, and C. tribuloides on both coasts of
the Athmtic. Fine specimens of the hxtter measure five inches across the si)ines.
Dorociduris papilluta occurs at depths of from one hundred to six hundred fathoms, and
has extremely long flvited spines, so that an example with a test about an inch across
will measure eight or nine inches from tip to tiji of spines. It occurs in the Mediter-
ranean, and the Atlantic, while examples collected at the Philippines cannot be dis-
tinguished from it. D. bracteata, a Pacific species, has the flutes of the spines set with
serrations.

In the species of PhyllacantJais the spines are often ornamented with frill-like
lamelltB, but vary greatly in shape and decoration. P. gigantea, of the Sandwich

Islands, has ten
spines in a series,
and six or eight
lamell* on each
spine. Gonioci-
daris ccmalicula-
ta is a species with
elegant s j) i n e s,
tolerably abun-
dant in the south-
ern ocean. It has
been dredged in
sixteen hundred
fathoms. In this
species the u])iier
part of the test is
quite flat, and the
two first series of
spines, which are
much larger than
the s]iincs of Cid-
aris usually are on
that i)art of the
test, lean over to-
wards the anal
opening, and form

an open tent for the protection of the young. These sjiiues are cylindrical and
nearly smooth, the outer series longer and shorter than the inner. A somewhat
similar ai-rangement obtains in Cidaris mdrix. Sometimes the young creep out,
with the aid of their first few pairs of suckers, ui)0n the long spines of the mother,
and return to the nuirsupium.

Porocidaris purpurata has several rows of peculiar paddle-shaped spines round the
mouth. These spmes arc flattened, longitudinally grooved, and serrated upon the edges.
Goniocidaris florigera is remarkable for the shajie of the jirimary sjiines set around
the anal area. These spines are dilated at the tip in such a manner as frequently to
form a flattened cnj>, equalling in width onc-thii'd the diameter of the test. The oldest
species of Cidaris occur in the Trias, and are small forms with smooth tubercles.

Fig. 145. — Cidaris nutrij:.

SEA-UllCHINS.

167

In the family Arbaciid.-e the median interambulacral spaces show as so many
bare bands, and the structure of the jaws, teeth, auricles, and s)tinos, is intermediate
between the CidaridiB and Echinidaa. The species are few. A. j^itnctulata occurs
upon the eastern, and A. nifjra ujion the western coast of this country. In delopleurKS
the spines of the primary tubercles are immense, three times as long as the diameter
of the test, and taper gradually to a fine
point. One species occurs on the coast
of Florida.

The Salenid.e are a small tribe with
spines like those of the Cidarida; in struc-
ture ; and with the anal and genital
plates soldered together. Sahnia vari-
spvici is quite common in the Cariljbean
Sea at depths from three hundred and
fifty to one thousand six hundred and
seventy-tive fathoms. This species has
a small purple body and Idug white ser-
rated spines, and in ajtjicarance resem-
bles Dorocidaris. The character which
removes it into another family seems a
very small one, yet is one in which it
differs from all regular sea-urchins, ex-
cept its own immediate relatives, which,
so far as we know, commenced to live
ii])on this earth in Jurassic times, and
have continued through cretaceous and
tertiary to the present day. Instead
of having five ocular and five genital
plates in its rosette, this little urchin has
eleven, the additional one large, cres-
cent-shaped, and occupying a central
position. This' plate thrusts the anus
quite out of the centre of the rosette.

In the DiADEJiATiD^ the spines are
hollow, long, and set with rings or ver-
ticillations. The test is thin, and the
spines delicate, so that it i§ very diffi-
cult to preserve a specimen entire. D.
mexicanus occurs on the west coast of
Mexico, while D. setosimi is found in
both oceans. In Eddnotlirlx the test is stouter than in Diadema, and there are many
vertical rows of very small tubercles instead of the larger tubercles of uniform size
which characterize Diadema and Astropi/i/a. E. desorii of the Pacific and Red Sea
attains a diameter of about five inches, while the spines do not exceed half the
diameter of the test, and are often banded with greenish yellow.

In Astropi/ga the test is so thin as to be more or less flexible, and is greatly de-
pressed, the height usually not exceeding one-third, or even one-fourth of the diameter.
In life the colors are very bright, the ambulacral 2Jlates have pits or de|)ressions of a

Fni. Wo. — Salenia vririsplna, enlarged.

168

LOWER IN VER TEDRA TES.

brilliant sky-blue, and the sj)ines of A. pulvinata are Hesh-colored, with brownish,
purple bands. The species named occurs on the west coast of Central America and
Lower California.

The EcHiNOTiiUEiD^ are a family distinguished, among other peculiarities, by the
flexibility of the test. This flexibility results from the arrangement of the plates ;
which, instead of meeting and uniting at their edges, overlap, arc separated by mem-
brane, and are thus free to move. Prof. A. Agassiz points out that this character is well
developed in Astropt/i/a, which may be considered as a connecting link between the
Diadematidre and Echinothuridse. The latter also present many points of resemblance
to the extinct PalKechinidfe. All the species have extremely dejtressed tests, resembling
at first sight those of a cake-urchin or Clyjicastroid, a group which they also simulate
in the comparative shortness and small size of the spines. In structure they are, bow-
ever, regular sea-urchins with the oral and anal systems on o)>])osite sides of the test.

M

l^th< nobomn ki/strU\

The genus Asthenosoma contains six species, and occurs at various dejjths from ten to
foiu'teen hundred fathoms. Although the test is so depressed in preserved examjjles,
living specimens, even when brought uj) from the moderate dejith of one hundred
fathoms, are nearly globular, as if the test had been blown up like a foot ball. In
PJtormosoma, of which seven species are known, there is in life a great contrast
between the flattened oral side, and the high and globose anal aspect of the test.
P. luctdentimi is perhaps the most striking species of the group. The test is of a
beautiful light violet, forming a brilliant contrast to the white lines, indicating the
sutures of the coronal jilates, to the comparatively long, smooth, shining, primary
spines, and to the silvery white, thick, hoof-like tips that terminate many of the primary
spines on the oral surface of the test.

The structure of the ))lates uj)on the area round the mouth, which remains flexible
in all echini, is in this family so similar to that of the j)lates of the test itself, as to
Buggest that they are jtrimarily of similar nature.

SEA-URCHINS.

169

Sir W. Thomson gives a grapbie accouut of the siiiprise occasioned by the move-
ments that passed tlirough the test of Asthenosoina hi/strix as it assumed upon the
deck what seemed its usual form and attitude. The test moved and shrank from
the touch when handled, and felt like a star-fish. It is quite dangerous to handle the
species of this family when alive, as the wounds they make with their numerous sharp
stinging spines jiroduce a j)ain and luunhness as unpleasant as tliat occasioned by the
stinging of a Portuguese man-of-war. The tests of some species (as jt^. teiiue) attain a
diameter of six inches. This species has been taken in two thousand seven hundred
and fifty fathoms. Judging from the large size of the eggs and of the genital openings,
this group of sea-urchins is probably viviparous.

The largest family of regular sea-urchins is that of the EcHiNiDJi, which may be
divided into the two groups of Echinometrida', in which the pores of the ambulacral
areas are arranged in arcs of several pairs of jjores, and Echinidie proper, whicli have
arcs consisting of only three pairs of pores. This difference is greater than it seems,
for the mode of growth of the bands of pores is quite unlike in the two groups.

Colobocentrotus atratus is covered by a pavement of closely packed hexagonal
spines, completely concealing the surface of the test. Those at the edge of the test
are rather longer and cylindrical or club-shaped. This species occurs at the Bonin
Islands, adhering to the perpendicular faces of rocks exposed to the ocean swells. In
this genus, as also in Heteroeentrotus and Echinometra, the outline of the test, viewed
from above, is el-
liptical. The two - ' -^
species of Hetero-
eentrotus have im-
mense club-shaped
or angular spines,
frequently twice as
long as the trans-
verse diameter of
the test ; certainly
the most striking
productions in the
way of spines to be
found in the entire
class. These spines
are a p p a r e n 1 1 y
smooth, but actu-
ally finely striated.
Those immediately
round the mouth
are liattened, while
on the upper sur-
face of the test the
secondary spines

sometimes lorm a fig. us. —. S'«roiigy(r>Cf H(ro(a.s dcodacAiensis, New England sea-urchiu.

close p a V e m e n t.

The auricles are tall and slender, with a large opening. Both species inhabit the

Pacific and Indian Oceans, spreading eastward us far as the Sandwich Islands.

170

LOWER INVERTEBRATES.

H. mammilatus has ten to eleven pairs of pores iu each arc, while JI. trigouarius has
fifteen to seventeen pairs. The spines of the former are usually stout and bat-shaped,
and in color vary from uniform ash-gray or light lirown, with white wings at the end,
to nearly black. In II. triyoiiarius the spines are usually longer, tapering, and more
or less triangular, but Agassiz states that they vary so much that the two species
cannot be distinguished by the spines. When a spine of II. mammilatus is broken
off at the base, it is replaced by a long tapering triangular spine like that of the other
species.

The genus to which the cumbrous name of Strong yloceiitrotics has been given con-
tains species with a circular or pentagonal, slightly depressed test, with pores arranged
iu arcs of at least four or five pairs. There are several species, of which the best

known is the S. driibacJdensis of the
north-eastern coast of North America,
and of Alaska. S. inexicanus occurs
in the Gulf of California, and the test
reaches a diameter of nearly three
inches ; but these dimensions are far
behind those of S. frauciscanus, of
the west coast of the United States.
In this form the test alone is five or
si.x; inches across, and the spines are
large, so that fine examples measure a
foot. In the Eehinidse projier, a grou})
which contains several genera and
species, the test is often nearly globu-
lar, — in Ainbh/pneustes the height
equals the width. Eddnus esculentii.i
is one of the best known forms, and is found on the coasts of Norway and of England.
The test is of a brownish or brick red color. As its name implies, it is occasionally
used as food. Ilvpponoe depressa. is a large species from the western coast of Mexico
and the Gulf of California.

Prioneclunus sagittk/ev, a species found by the 'Challenger' expedition at depths
varying from seven hundred to one thousand and seventy fathoms in the seas around
Australia and the East Indian islands, is remarkable fi-om the presence upon the spines
of serrations resembling those of Salenia variapina, instead of the regular Huting
characteristic of most Echinid;e.

Fig. 149.

-Echinus escuhtiiuSy tlie spiues removed from
halt of the test.

Order II. — CLYPEASTRID^E.

In this order the mouth is ])laeed as in the regular sea-urchins, but the anal open-
ing occupies a j)osition immediately opposite to the odd ambulacrum, and often on
the under side. The genital pores retain their position at the summit of the upper
surface of the test, which is exceedingly depressed, with its edge or ambitus more or
less sharp, so that the upper and under surfaces are entirely cut off from each other,
and are of quite different character. The rows of pores for the exit of the suckers
do not extend around this sharp edge, but form five ])airs of curves, arranged some-
Avhat like the ])etals of a flower, upon the upper surface only; while on the oral
surface the ambulacra are marked by furrows that converge toward the mouth. The

SEA-URCHINS.

171

pores upon the oral surface are cither scattered widely over the ambulacral and some-
times over the inter-ambulacral jilates, forming joore arece, or they are arranged in
bands which ramify over both the ambulacral and the interamlnilacral i)lates. Tlie
difference between the anterior and posterior extremit}' is well marked in tliis order,
the former being known by the odd ambulacrum of the three ambulacra composing
the trivium, the latter by the position of the anus between the posterior pair of ambu-
lacra or bivium.

The jaws of the clypeastroids are much sim]i]er than those of the regular echini,
and articulate upon the auricles, instead of being held injilace by muscles, as in the
latter. They are V-shaped, and are placed horizontally. The teetli are secured in a
groove corresponding to the line of junction of the arms of the V. The spines are
in all eases delicate and short, often almost velvety in their fineness. The water system
of the clypeastroids is without Polian vessels, but there are large vesicles at the
bases of the suckers. The species mostly live upon sandy or muddy bottoms.

In the EucLYPEASTRiD.E the upper and lower floors of the test are connected and
strengthened by pillars, needles, or radiating partitions of calcareous matter. J^chi-
nocyamtis xnisillus and a few other sjjecies are almost as globular as the Echinidae,
but are true Clypeastroids in structure, with simple partitions extending inwards from
the circumference. In Clypeaster and Ecldnanthus the floors are connected by jiillars,
slender in the former genus, massive in the latter. The species are large, and, though
flattened, have a rounded ambitus, while the oral surface is concave. C rotundas
occurs on the west coast of North America, as far north as San Diego, while Echi-
itanthus rosaceus is tolerably common about the West India Islands and Florida.
Laganurn and its near relatives have the floors connected by walls that run parallel
to the edge of the test.

In the ScuTELLiD^E the test is extremely flat, and is usually more or less circular.
The great quantity of calcareous matter forming the flattened edge is in many species
lessened somewhat by the presence of
cuts or oj)eniiigs in the ambulacral or
interambulacral areas. The furrows
of the under surface, which are straight
in Cli/2)eaiiter, are in this grou]) more
or less branching, and the upper and
lower floors are supported by parti-
tions that radiate from single points.

Some of the best known forms of
Scutellidae belong to the genus EcJii-
7iarachnius, and are without cuts or
lunales. E. parma, the Sand Dollar,
is found on the Atlantic coast of the
United States, and also on the Pacific
coast as far south as Vancouver Island,
and in Asia as far as Japan. E. ex-
centricus is the common cake-urchin
of the Pacific Coast, from Monterey
northward, and occurs also in Kamts-

chatka. It is very common in San Francisco Bay, where
a depth of five to seven fathoms.

Fig. 150. — Echinarachnius parma, saud-dollar.

lives ujion the sand at

172

LOWER INVERTEBRATES.

In Mellita the test beeomes large and heavy, and the edges present deep cuts
opposite to the ambulacra. In JEncope the massiveness of the test increases, reaching
its fullest development in E. (/randis, a native of the west coast of Mexico and of
the Gulf of California. It is hard to lielieve that the mass of calcareous material
forming the test of this sea-urchin ever contained a living animal. The edges of the
test are half as thick as the thickest part, which is at the anus. There is a huge
lunule between the posterior ambulacra, beside live cuts opposite the ambulacra.

Order III. — PETALOSTICHA.

These sea-urchins, more commonly known as irregular sea-urchins or Spatangoids,
have no dental apparatus ; the test is variable in form, though usually more or less

elliptical; and the anal system is placed between the two posterior ambulacra (bivium).
Certain parts of the test and spines are greatly specialized ; and the radiate form is
accompanied with an evident bilaterality.

Neither the oral nor the anal apertures are in the centre of the test, the former
being displaced anteriorly, and situated beneath the odd anterior ambulacrum, while
the latter is situated beneath or between the petals of the bivium. The ambulacra in
this order vary greatly, but are always petaloid in character upon the upper surface,
the series of pores not being continuous around the edge of the test to the under
surface. The anterior petal or ambulacrum often becomes more or less abortive,
so that there are only four petals visible above; while in other cases it is much
enlariied.

SEA-URCHINS. 173

The spines of the Petalosticha vary greatly in size, not only in different species,
hut in the same indivichial. They are always delieate and sdky, though in some
species they may he of great length. When the test is cleaned, its surface is in many
cases found to be marked by one or more symmetrical bands of close-set tubercles,
so small that a powerful lens is needed to distinguish them. During life these
tubercles bear slender spines, the heads of which are enlarged, while the shafts .ire
set with cilia, and shaft and head alike are covered with a thick skin. These fascicles
lie beneath or around the anus ; they surround the outer extremities of the petaloid
ambulacra, or, as in Amphidotus, they encircle the inner or apical terminations of the
ambulacra.

Fascicles, as such, are recognized only among spatangoids, but it is probable, says
Prof. Agassiz, that the accumulation of miliary tubercles on the edge of some Phor-
mosomas must be regarded as the first trace of them. The earliest spatangoids, like
the Dysasteridae, have no fascicles.

Throughout all these changes of position of mouth and anus, the genital and
ocular plates retain their central position; but in some genera the genital orifices are
reduced to four.

The circular ambulacral vessel in this order has no Polian vesicles, and there are
no vesicular apjiendages to the bases of the jiedicels or suckers, of which there are four
kinds. These are single locomotive pedicels without any sucking disc; locomotive
pedicels containing a skeleton, and provided with terminal suckers ; tactile pedicels,
with papillose, e.xjianded lips; and triangular, flattened, more or less comb-like lamellae.
Two or three of these kinds of feet may occur in any ambulacrum, and those which
occur upon a fascicle are always different from the others.

In the Cassidultd^ there are no fascicles, and the form of the test is sub-globular,
ap]iroaching that of the regular echini. It includes the sub-families Echineinre and
Nucleolinjie.

The mouth in this grouji is placed centrally, or near the centre. Rhyncopygxis
parjficuit of the western coast of Mexico belongs here, as does also Catopygus recens,
which was found at a depth of one hundred and twenty-nine fathoms south of New
Guinea, and has an elevated test, the height about equal to the width, heart-shaped
when looked at from behind, and pointed in front.

In the Spataxgid.e, the principal family of the order, fascicles or bands of
crowded miliary sjjines occur, and a plastroii, or space without large spines, surrounds
the oral opening, and is bordered by pores. This group is divided into several others,
the Pourtalesiw, Ananchytina?, Spa-
tangina, Leskiina?, and Brissina, all
distinguished itiainly by peculiarities
in the petals and fascicles.

In Pourtalesia and its allies the
ambulacral sj-stem is simple, and the
plates which compose it are large.
The mouth, a large opening situated
in a groove, is elliptical, and is cov-
ered by a membrane strengthened by Fw.K2.-Pnnrinir,ia jefreysu.
an outer row of jilates. The species

of Pourtalesia have a curious snout, on the upper side of which the anal opening is situ-
ated. This snout gives to the test a most peculiar appearance when viewed from the

174 LOWER INVERTEBRATES.

side, while, viewed from above, some have a more or less bottle-shaped outline, and
others are triangular. P. tniranda has been dredged in the Florida Straits, and near
the Shetland Islands.

P. carinata is a large S]iecics with a rather stout test and a bottle-shaped form. It
IS about four inches long, of a light claret color with whitish pink sjiines, and is
a native of deep water, as it was dredged .at from sixteen hundred to two thousand two
hundred and twenty-five fathoms in the Antarctic Ocean. P. ceratopnga is remarkable
for the great width of the anterior extremity and the narrowness of the anal snout,
giving to the test a triangular shape. Viewed laterally and in the reai', the posterior
projection has considerable resemblance to the head of a turtle. It occurs in the same
localities with the preceding species, and, judging from fragments of some large speci-
mens, must attain a length of aljout seven inches. P. hispida has a very short anal
snout, and the shape, viewed from above, is that of a short, broad bottle. The trans-
verse section is rounded, instead of obtusely triangulai-, as in the last species. P.
htgancula and P.phiale are both bottle-shajied species, more or less circular in transverse
section. The former occurs both north and south of the equator, from three hundred
and forty-five to two thousand nine hundred fathoms, while the latter, which is a pecu-
liarly slender and small species, was found in 62° 2G' south latitude, has an extremely
thin test, and is of a light yellowish jiink color. A peculiar form related to Pourta-
lesia is Spatangocystis challengeri, in \\ hich the anal snout is a small projection at the
posterior end of a sharp keel which runs along the under side from the mouth back-
wards. In Echinocre^ns cuneata^ the general outline, whether viewed from above,
laterally, or endwise, approaches a triangle, and there is no anal snout, the anal system
appearing on the lower or actinal surface. The two last forms were both taken in
deep water in the southern ocean. Other southern Pourtulesim without an anal snout
are Urechiniis naresianus and Cystechinus, of which two species, vesica and leyinllii,
are known. C. vesica is the only spatangoid thus far known, which can evidently
expand and contract its test. Cystechinus is elliptical in plan and irregularly trian-
gular in profile.

Calynere has simple ambulacral pores ; two of the ovaries are in the trivium, and
the others are not developed. Its outline is elliptical, and there is a slight keel on
the under surface. C. relicta has been taken at Tristan d'Acunha, and near Fayal, in
two thousand six hundred and fifty fathoms. The central portion of the oral surface,
and the apical surface near the posterior pole, has groups of paddle-shaped spines.

To the Ananchytina3 belong, besides many fossil forms, a few recent genera, among
which Ilomolampas has very rudimentary petaloid ambulacra, a flattened test, and a
well-developed sub-anal fasciole. H. fulva is about four inches long, of a light straw
color, and heart-like in shape. Large curved sjiines are scattered at intervals among
the short ones that cover the test. It was dredged in two thousand four hundred and
twenty-five fathoms, by the 'Challenger' expedition.

To the Spatanginfe belong the typical tS])ata))gus, species of which are common in
Europe, and the nearly allied 3Iaretia and Lovenia. Lovenia cordiformis is elongate,
heart-shaped, flat upon the oral surface, and provided with numerous very long prim-
ary spines, half as long as the test. It occurs on the west coast of Mexico and in Cali-
fornia as far north as Point Conception. Here also belongs the fine species lireynia
australasice, which attains a length of four inches and a width of more than three, and
is found in China, Australia, and Ja]ian, an<l also Echinocardium cordatum of both
coasts of the Atlantic.

SEA-URCHINS.

175

-Brood pouch of Ht'miastcr ph'Uippli contaiuing eggs, enlarged.

In the swb-family Rrissiii;i, the oviuis Ilemiaster is one of the most iuterestiiiij, on
account of the manner in which it carries its young, which develop without a metamor-
phosis, in receptacles on the ajiical surface.

11. phibppii, a somewhat heart-shaped species found at Kerguelen Island, has
certain of the ambula-
cra! plates greatly ex-
panded and depressed,
so as to form four deep,
thin-walled, oral cujis
which encroach ujion
the cavity of the test,
and form marsupia or
brood-pouches for the
protection of the
young. The spines
are so arranged that a
kind of covered way
leads from the ovarial
ojiening to the pouch,
and in this passage the
eggs are kept in place
by the spines, two or three of which bend over each egg. In this way they are jjassed
to the mai-supium. The embryos stay within the pouch until the plates of the test have
developed. Young echini in all stages of development are formed within the pouch, and
the small ovaries contain some weU-de\-eloped eggs ready to eseajie into it as soon as
there is room. In the young the anal opening is nearh' central, so that it looks almost
like a regular urchin. H. cavernosus is regarded by Agassiz as identical with IT.
2}hil/ippii, but If. zonatus and // gihbosus are distinct.

Aeropiese rostrata is remarkalile for its length and narrowness, for its dee2ily sunken,

odd anterior ambu-
lacrum, and for the
eight great sucking
discs upon the lat-
ter. Aceste bellidi-
fera is near Aerope,
yet is in appearance
one of the strangest
of sea-urchins, for
nearly the whole of
its upper surface is
occupied by the
deeply sunken odd
anterior ambula-
crum, surrounded
by a narrow fas-
ciole, from within

which spring large, flattened, paddle-shaped spines. These spines curve over the great
hollow of the ambulacrum, and underneath them may be seen a number of huge disc-

Fir.s. I;i4 and lo5. — Upper and under surfaces of Ac^\^te hellidifera.

176 LOWER INVERTEBRATES.

shaped suckers. Tlie excretory opening is at the posterior extremity. Only two
ovaries are develojied, and the eggs appear to be very large at the time of expulsion,
corresponding to the large size of the ovarial openings.

The genus Schizaster includes several species of almost circular outline when
viewed from above, but with a deeply sunk anterior ambulacrum, and the other ambu-
lacra depressed. In the young the odd anterior ambulacrum, as in Accste, occupies
the greater part of the ujjper surface, and the suckers of this ambulacrum are very
large. Thus, Aceste may be regarded as a permanent form of the young of Schizaster.
Other Brissina are the well-known large species Drissns carinatus^ which is widely
spread in the Pacific, and reaches a length of seven inches, and a width of nearly six ;
the pretty little egg-like and delicate Agassizia scrobiculata of the west coast of
Mexico, and Perinopsis lyrifera of European seas.

Class IV. — HOLOTHUROIDEA.

The Holothurians or Sea Cucumbers are the least radiate and least typical of
echinoderms, approaching the worms in the length and usually cylindrical form of the
body (which is elongated in the direction of the axis), of the oral and aboral systems,
and is without arms. The mouth is surrounded by a circle of branched tentacles, and
the body-wall is muscular and leathery, instead of presenting a calcareous test or
system of calcareous plates or ossicles, as is the case with other echinoderms. But
though there is usually no continuous calcareous armatui'e, the integument contains
numerous calcareous bodies of varying form. The body-wall consists of an external
skin, within which is a layer of connective tissue, and inside this a layer of muscular
fibres, some of which are disj)osed in circles around the body, while others form five
longitudinal bands. These bands are attached to a calcareous ring surrounding the
mouth. The calcareous plates forming this ring are ten or twelve in number, and the
longitudinal muscles are attached to five of these. These five plates are also notched
for the passage of the nerves and ambulacra! canals.

The water-system varies greatly in degi'ee of development. In one section of the
class (Apoda) there are no ambulacral feet or ambulacra! canals, and the only trace
of the water-system is to be found in the ring-canal round the gullet, with its greater
or less number of Polian vesicles internally, and the circlet of comparatively simple
tentacles externally, and in the madreporic or stone canal or canals, which run down-
wards into the body and terminate in a calcareous network, the homologue of the
madreporic body of other echinoderms. In .all the class, with two exceptions, the
madreporic body is internal, and by its openings the water-system communicates, not
with tlic external water, but with the large body-cavity that intervenes between
the intestinal canal and the body-wall.

In the higher Holothuria or Pedata the circular vessel of the ambulacral system
not only gives origin to the Polian vesicles, stone-canals, and tentacles, but to five
ambulacral canals, which pass through holes or notches in the plates to which the
longitudinal muscles are attached, and run backward along the median line of each of
those muscles, immediately interior to the longitudinal nerve. In most cases each of
these ambulacral vessels is furnished with ampullae, connected with processes of the
body-wall which form suckers or ambulacral feet, much as in a sea-urchin. In other
genera some of the rows of suckers are suppressed, the other rows forming a surface
upon which the animal creeps.

HOLOTHURIANS.

177

There is nn dentnl apparatus in the lioh)thiiri(ls, but a short ]iharynx leads into a
stomach, and this into an intestine usually much longer than the body, and often
several times its length. In the
higher holothurids the intestine
terminates in a distinct chamber
or cloaca, often of large size. Into
this cloaca open the stems of two
(sometimes one) hollow, much-
branched organs called the 'res-
piratory trees.' The sea-water
enters into and is expelled out
of these organs, which thus fill
the body-cavity with water that
is taken up by the madreporic
body and carried into the water-
system. The resj^iratory trees
are also believed to be organs of
excretion.

In some holothurians the
cloaca or the respiratory tree is
also jirovided with simjile or
branched appendages the interior
of which is occupied by a solid
or viscid substance. The use of
these is not certainly known, but,
as they are readily thrown out
when the animal is disturbed,
Semper supposes that they are
organs of defence. These are
known as the Cuvierian organs.

The nervous system is of the
usual echinoderm pattern, consist-
ing of a mouth-ring ]>laced above
the ring-canal of the water-system,
and of five princijial ambulacral
cords passing through notches in
the plates around the cesophagus.
The system which is supposed to
be analogous to the circulatory
system of higher animals is very
complex in many of the higher
holothurids, extends over the ali-
mentary canal, and enmeshes one
of the respiratory trees.

The genital organ is in many
cases single, and in the Synap-
tidas contains both ova and sper-
matozoa, so that these forms are

VOL. I. — 12

Fig. 156. — Anatomy of Caudina arenata ; a, anastomoses of dorsal
blood-vessels; h, branchial tree: rf, dorsal blood-vessel; /, mesen-
terial filaments; //, genital opening: i. alimentary canal; /, longi-
tndinal muscles; m, mouth; o, genital duct: p, pharyngeal ring;*
r, reproductive organs, cut away on right side; t, tentacular am-
pullae; r, ventral blood-vessel.

178 LOWER INVERTEBRATES.

hcrmajihrorlitc. In the mnjority of the clnss the sexes ave distinct. The oviduct opens
near the mouth. The ovum, after segmentation, becomes, by the invagination or turn-
ing inwards of a part of tlie external surface, converted into a hollow gastrula, the
opening of which becomes the anus, while a mouth and gullet are produced by the
invagination of the outer layer of tissue or ectoderm. The comj)leted alimentary canal
of the larva consists of a gullet, a rounded stomach, and an intestine, and the cilia of
the external surface become restricted to a number of hoops or bands, from one to five
in number, bent upon themselves, yet passing all round the body. These arc accom-
panied by certain ear-like projections, from which tlie young is known as an Auricularia.
Before the auricularia is fully formed the young holothurian buds out near the side of
the stomach, and gradually develojis its spicules. The ear-like jirocesses disappear, the
auricularia becomes cylindrical, the body of the embryo elongates, tentacles are devel-
oped around the mouth, and the young holothurian is complete. The entire course of
development is largely jiarallel to that of the other echinoderms, but the holothurian
is more directly developed from the larva than is the case in sea-urchins and star-
fish. Some liolothurians, like some star-fishes and sea-urchins, have the larval
stages suppressed or only slightly indicated, the young devclojiing in a sort of
marsupimn.

The holothurians are of little economic value, and with us are regarded merely as
objects of scientific interest. In the East they are more important, and as 'trepang'
play a prominent part in the diet of the Chinese and other oriental pcojiles. The
trade of preparing the trepang is almost entirely in the hands of the Malays, and every
year large fleets set sail from Macassar and the Philijipines to the south seas to catch
the ' Beche-de-Mer.' They are split open, boiled, dried in the sun, and then smoked
and packed in bags. The annual catch is estimated at about four hundred tons, and
the price varies according to quality from seven to fifty cents a pound. Trepang is
very gelatinous, and is used as an ingredient in soujjs.

Although the holothurians must evidently be classed with the PZchinoderms, their
simplest forms, as Eupyrgns, present nothing of the radiate arrangement except the
circle of tentacles; and their affinities to such worms as Sijncncidus and its allies,
which have also a complete circle of tentacles, a ring-canal, and a kind of water-system,
seem in many respects close.

The Holothuroidea have Ijeen said to feed on living coral, but this seems disproved
by recent observations. The manner in which they feed is well illustrated by the
following account of the habits of a species of C'ucumaria, common upon the coast of
Cornwall. When in full feed the tentacles were obser\-ed to be in constant motion,
each separate tree-like plume, after a brief extension, l)eing inverted and thrust bodily
nearly to its base in the cavity of the pharynx, bearing with it such fragments of sand
and shelly matter as it had succeeded in grasping. No particular order was followed,
but the meal continued for hours. One might imagine a child with ten arms, like
an ancient Buddha, grasping its food with every hand, and thrusting hand and arm
down the gullet with each handful. These animals were kept in a tank with living
corals without in any way interfering with them. The nutriment must be furnished
by the Infusoria, diatoms, and other microscopic animals and vegetables which
always more or less cover the debris at the bottom of the water. Probably the
shell or coral debris is triturated by the teeth of the pharynx. It has been calculated
that fifteen or sixteen of these creatures will remove about eighteen cubic feet of coral
per annum.

HOLOTHURIANS. 179

Order I. — ELASIPODA.

The Elasmapoda, or Elasipoda, are true deep-water forms, none of which are
known to exist at a less depth than fifty-eight fathoms, at which level Elpidia
glacialis has been taken in the Arctic Ocean. The same species has been dredged
in warmer seas in two thousand six hundred fathoms. The first example of this group
was discovered in the Kara Sea over seven years ago, but from the results of the recent
deep-sea exploring expeditions over fifty species are now known.

In the Elasmapoda the adult and larval forms agree more closely than in other
iiolothuroids, and they are therefore placed by some naturalists low in the scale, while
others place them high on account of the distinct bi-lateral symmetry of their bodies,
the well-marked distinction of the dorsal from the ventral surface, and the frequent
specialization of a cephalic or 'head ' portion. The ventral ambulacra; alone are fitted
for locomotion.

]xolga hi/alina is a sniall example of the Elasmapoda, with the oral disc facing the
ventral surface, and the anal orifice facing the dorsal surface, thus producing an arrange-
ment similar to tliat which prevails in the star-fishes and echini. The anal orifice has
a dorsal collar, Ijearing sucker-like contractile [lajiilla-, communicating with the body-
cavity instead of with the water-system. The sand canal (stone canal), instead of
hanging free within, opens on the exterior in front of the dorsal collar. This is simply
a persistence of the condition of things found in the larvfe. Two other genera, Tro-
chostoma and Ir^ya, have the outer end of the sand canal attached to the skin, with a
madreporic plate at the point of attachment, but the canal does not communicate with
the exterior. In Elpidia the arrangement is similar, but the madreporic plate is rudi-
mentary or wanting. Kohja is dicecious, l)ut has no respiratory tree. The two dorsal
nerve-trunks furnish an offshoot to each of a pair of large vesicles containing otoliths
— a rudimentary organ of hearing.

Order XL — APODA.

In this order there are no ambnlacral feet, and the water-system is therefore re-
stricted to the ring around the gullet, the circlet of tentacles around the mouth, and
the canal communicating with the madreporic body. The Apoda are again divided
into the Apneumonia, which are destitute of a respiratory
tree, have no proper cloaca, and are without Cuvierian
organs, and the Pneumophora.

The simplest of the footless holothurians without
breathing organs, and, indeed, the simplest of all known
holothurians, is Eupyrgus scaber, a species less than half
an inch in length, provided with a circle of fifteen un-
branched tentacles round the mouth, and covered with soft
papilliE bearing calcareous plates. The longitudinal muscles
are weak and small. It is an Arctic species, and has been
taken on the coasts of Labrador, Greenland, and Norway. Fig. 157. — ■ wheel ■ from skin of

Mijriotrochus rinkii has also been found in shoal water ' ^"^"^

on the coast of Labrador, and lias a transparent skin dotted with minute white spots.
These spots, when magnified, are seen to be wheel-like calcareous plates.

180

LO WER IN VER TEBRA TES.

Another very worm-like .s])eeies, eoinnioii in Labrador, iis Chirodota Icp.ve. It is

whitish-gray, with wlieel-like jibites, like the last speeies, showing as white spots.

The two last mentioned species belong to the family Synaptid^e, in which the

sexes are nnited in the same individual, the tentacles are finger-like, or lobnlated,

and the form elongated and worm-like.

In Synapta the integument contains numerons ])erforated, flat, calcareous plates,

\<i which arc attached ])rotruding anchor-
like hooks. Mijriotrochus has a single
I'olian vesicle, but Synapta has several.
Syiiupta girardii is a common species njion
the Atlantic sea-coast, living in sand at low
tide level. Its exceedingly attenuated body
breaks uj) into several jjieces when the ani-
mal is disturbed. Synapta similis is said
to live in brackish water. Synaj^tulK vici-
■para is one of those sjjccies in which the
young develoj) directly, and are protected
in a marsupimn.

OliyotrocJius ritrei/s is a species living
at depths of from fifty to two hundred
fatlionis on the coast of Norway, less vermi-
form than Si/iiapid, since its length is only
about four times its thickness, and sluggish
in its motions on account of the slight con-
tractility and stiffness of its body, which
is transparent and colorless. The tentacles
are twelve in number, and are less devel-
oped than even in Chirodota. The cal-
careous plates, which are wheel-like, are

very few, and deejily sunk in the skin. The calcareous ring round the gullet shines

snow-white through the 1)ody-wall, which also allows the intestines, generative organs,

etc., to be clearly seen.

The next sub-order (Pneumoj)hora) has a resjiiratory tree arising from the cloaca.

Cttudlna is so called from the long, tail-like prolongation in which the body ends.

The skin is rough externally, from the calcareous pieces iml)C(lded in it. C. arenata,

the only species, has fifteen four-])ronged tentacles, and is a somewhat common object

in Massachusetts Bay.

Molpadia turyida, is a dee]i-water form that has 1 icen taken in over a hundred fathoms

in the Gulf of Maine, and is known to range southward to Florida. It is a tailed species

with fifteen tentacles and an anterior extremity shaped like the neck of a bottle.

Most of the Ajioda are natives of the cold seas of the Arctic regions, but some

genera, as Synajjta and Chirodota, are almost cosmopolitan.

Fig. \m. — Synapta inhm-enft, with anchors and phates.

Okder III. — PEDATA.

The Pedata, as their name implies, are .always furnished with a greater or less
number of arabulacral feet; a respiratory tree is always present, and the sexes are
distinct.

HOLOTHURIANS.

181

In the Dendrochirotiv the tentacles are tree-like or branching, and there are no
Cuvierian organs. The pharynx has retractor muscles. Many of the species inhabit
northern regions. Pentactafrondosa, the
common sea-cucumber north of Cape Cod,
and extending through the Arctic ivgions
to Great Britain, is from six inches to a
foot in length, of a tan brown color, and
suggests a cucumber by its shape and the
corrugations of its skin. The pharynx is
muscular; the stomach short, with well-
marked transverse folds within ; the intes-
tine several times longer than the body,
and the respiratory tree with but one main
stem. Connected with the ring-canal are
two Polian vesicles, nearly two-thirds as
long as the body. The single ovary is
made up of a mass of long tubes, which
are larger than the branches of the res-
j)iratory tree, and are tangled up with
them. The genus Cucumaria, or Pen-
tacta, has many suckers in the ambula-
cral area, and some forms have them also
in the interambulacral areas. The body
is short and somewhat ti\-e-angled, and
there are ten tentacles, of which the two
belonging to the odd ambulacriun of the
bivium are often smaller than the others.

In Colochirus the feet are ranged in three rows upon the ventral surface, the
remaining ambulacra of the Itack havbig only pa23illa3. The two central tentacles of
the lower surface are smaller than the others. In C. cceruleus, from the Philippines,
the pai)illae of the back are very long.

In Psoitis the ventral siu-face is clearly separated from the rest, and there are no
suckers upon the ui)i)er surface. The surface of the body is covered with comjjara-
tively large plates, of which Psolus comjilanatus has fourteen to sixteen, in a trans-
verse row. This species and another occurs in the Philippines, P. squamatus is found
at the Kiirile Islands, P. phantopxs and P. fahricii in the Korth Atlantic, and P.
untarcticus in the Straits of Magellan.

The female of Psolus ephlppifcr has upon the up2>er or dorsal surface a group of
larijer tessellated plates, each carried, like the head of a mushroom, upon a pedicel
imbedded in the skin. The spaces left underneath these tiny vaidts are utilized for
the protection of the young, which develop directly into sea-cucumbers. The males
have the plates of the back similarly arranged, though there is no marsujtiura.

In Jliyone, Thyonidiuni^ and other related genera, the suckers of the entire body
are alike, and seldom show traces of arrangement in rows. Tliyonidiimi has five pairs
of large and five of small tentacles.

Tliyone hriareus lives just below low tide from Long Island Sound to Floi-ida, and
is very common. In a specimen little more than three inches long the alimentary
canal is about seven feet in length, though the oval stomach is less than an inch. The

Fig. 159. — Pi^ilttwta J'mndosa.

182

LOWER IN VER TEBRA TES.

tentacles can be deeply retracteil. There are three Poliau vesicles, the respiratory
trees divide at ouce into two very bushy branches, and the Cuvierian tubes foim a

brush-like tuft about an inch in

^.

C5

<;@'^

length.
^;,i, Vladodactyla crocea was found

^^I ^ adhering to the huge tangle in
fflS^ the southern seas, and is abun-
dant at the Falkland Isles. It is
of a bright saffron color. The
three anterior ambulacral vessels
are near together, and bear num-
erous well-developed sucking-feet
for locomotion, while the two am-
bulacra of the bivium are also
near together on the back. In
the females these latter ambula-
cra have very short, tentacular
feet, which, though jirovided
with sucking discs, seem, from
the rudimentary condition of the
I'osette of calcareous plates at
their tip, scarcely fitted for loco-
motion. In the males there is
rather less difference between the
dorsal and ventral ambulacra.
In the females the young were
found closely jKicked in two con-
tinuous fringes adhering to the
water-feet of the doi'sal ambula-
cra. " Some of the mothers with
older families," says Sir Wyville Thomson, "had a most grotesque appearance, — their
bodies entirely hidden by the couple of rows, of a dozen or so each, of yellow vesicles
like ripe, yellow plums ranged along their backs, each surmounted by its e.\])anded
cro\vn of oral tentacles."

In the Aspidochirotoe, or holothurians with disc or shield-shaped tentacles fur-
nished with tentacular am])ull.Te, the left rcs]>iratory tree is bound to the body-walls,
there are no retractor muscles to the pharynx, and Cuvierian organs are jiresent.
These are the highest type of Holothuroidea, and are mainly tropical in their dis-
tribution.

In Stichojms the tentacles are eighteen or twenty in number, the body is more or
less quadrilateral in section, and the ambulaeral feet project from papillie. Three
distinct rows of these can usually be traced upon the flat ventral surface. /iS". varie-
f/atus, which has been found at the Samoan Islands, and at the Pliiliii])ines, attains an
enormous size. Examj)les three feet or more in length, and eight inches thick, ha\e
been taken.

3fulleria has five calcareous plates or teeth at the anal extremity.
In the t}-]iical genus IlolotJnn-ia the feet are scattered all over the surface of the
body, usually without distinction into rows. Some of the species attain large dimen-

FiG. 160. — Psolus fabrtcHt showing under surface with tliree rows
of ambulacra.

HOLOTHURIANS.

183

sions. H. marmorata, from the East Indian islands, Fijis, etc., reaches a foot in
length, and II. tenuissima attains a length of two feet, and a thickness of six or seven
inches.

In some species of Holothwia, as in H. marmorata, the ambulacral processes of the
lower surface only are truly ambulacral feet, the others are papilla; : in another group,
including II. tenuissima, the suckers or papillas are all alike, and in still another the
ambulacral feet upon the ventral surface are much closer together than those upon the
back.

Holothuria floridana is abundant on the Florida reefs just below low-water mark,
and reaches a length of fifteen inches. The calcareous pharynx leads to an alimentary
canal which is about three times the length of the body, and ends in a large cloaca.
The branch of the respiratory tree which is attached to the body-walls extends to the

- Clailmlacti/lii rroren.

pharynx. The Polian vesicles are numerous, the largest an inch in length, and the
madreporic body has upon it a group of about thirty stalked processes, the largest
about a quarter of an inch in length. The tentacular ampulla; are twenty in number,
lono- and slender.

Order IV. — DIPLOSTOMIDEA.

This order, or sub-class, established by Semper to contain the singular Rhopalodina
lageniformis, is characterized by a nearly spherical body, with the mouth and anus
close together, and ten ambulacra. Semper regards it as the type of a fifth class of
echinoderms.

Rhopalodina lageniformis has a flask-shaped body, and the mouth and anus are at
the narrow end of the flask, the former surrounded by ten tentacles, the latter by ten
papillae and by as many calcareous plates. A ring of ten calcareous plates surrounds

184

LOWER INVERTEBRATES.

the gullet, and between the latter and the cloaca the genital disc is situated. The ten
ambulacra diverge from the centre of the enlarged or aboral end of the body, and ex-
tend, like so many meridians, to near the neck of the flask. Each ambulacrum has
its own longitudinal museul.ar band, five of which are attached to the circle around the
anus, and five to that around the mouth. The species is found upon the Congo coast.

W. N. LOCKINGTON.

Fig. 162. — Aucbors and plates of Synapta girardii.

WORMS. 185

Branch V. — YERMES.

The great and varied assemblage of animals which are put together under the
common designation of worms does not present a homogeneous group for study. On
the contrary many distinct types have been thrown togetlier to make the branch of
worms. Indeed it has been a long-standing current joke among zoologists that this
part of the zoological system was the garret, or as the German has it the Riimpelkam-
mer, into which everything was carelessly thrown that did not properly belong else-
where, and had been therefore rejected from the other portions of the system of classi-
fication. The worms have thus come to be a collection of forms whose outside affini-
ties extend to nearly all other animals, while among themselves they fall into classes
not closely related with one another. These classes shade off in some cases towards
other branches; thus the rotifers a jiproach in their organization the molluscan type,
while the Annelida proper show in some resjjects unmistakable similarity with the
insects. Other classes, like the Aeanthocephali and Enteropneusti {Baluiioglossus)
attain an anatomical configuration which gives them a certain indejiendence, a place
apart, in the zoological system. In brief, as the limits of the branch of worms are
vague, and its components multifarious, therefore it is difficult to defijie the worms
with an accuracy corresponding to the requirements of a rigorous science. The fol-
lowing definition is the most satisfactory I am able to give : —

A worm is a bilaterally symmetrical animal, with a distinct head characterized by
the presence of the principal nervous centre or so-called brain. It is distinguished
from molluscs by the absence of a shell and of that modification of the skin, named
the shell gland, which forms the shell and is present at least in a rudimentary condi-
tion in all true molluscs. It is distinguished from Crustacea and insects by the want
of jointed limbs, .and finally from the tunicates and vertebrates by the lack of a struc-
tural axis, the so-called notochord or chorda dorsalis, which gives the name of Chor-
data to the divisions last mentioned. As far as at present known no worm has a true
liver, a calcified internal skeleton, an organ homologous with the cndostyle of ascidians
and thyroid gland of vertebrates, any tracheal tubes like those jterforming respiration
in insects, or finally any unicellular haiis. In fact a ^^'orm must be recognized as such
rather by the process of exclusion than by the observation of positive characteristics.

To the scientific zoologist the worms are most interesting subjects of study, not
only from their manifold variety and strange life histories, but also from their relation-
s-hip with the higher tyjies, the ancestral forms of Avhich are with good reason sup-
posed to be more nearly represented by certain worms than by any other animals now
existent. The mind links in imagination these obscure and humble creatures with the
most exalted organisms, and finds in the secrets of their low organization the key to
the complex structure of the higher animals. We, however, shall not enter upon
these difficult discussions, where debate is still active, and the final decision uncertain.
Instead we shall be sufficiently occupied with studying the principal and most in-
teresting forms of vermian life as to their appearances and habits. Although a worm
is by popular fancy a loathsome thing, yet only some of them deserve opprobrium,
while many others are objects of great beauty, and others again are quaint ; a few ai-e
of great utility to man, and yet others are among man's most dreaded enemies.

186 LOWER INVERTEBRATES.

All worms appear to require moisture, ami the majority of them are aquatic, in-
habiting ponds and rivers and peopling the sea. The adults frequently exhibit a
marked preference for a living burial and inhume themselves in sand and mud, some
at the bottom of stagnant waters or running streams, others in the floor of the ocean
at all dejiths ; but they are found in the greatest variety and number on sandy
beaches, which the changing tides alternately cover and expose. Under stones or
sunken in the ooze tlie collector gathers them in astonishuig abundance. In the moist
earth, especially in vegetable humus, and in manured soil live the common earth
M'orms. Some species, like those of the genus tSar/itta, are called pelagic, for they swim
about upon the ocean surface in company a\ ith the embryos and larvas of worms of
many kinds and a marvellous society of other living things. Rotifers and others
swim in fresh water as well. Finally is to be mentioned the parasitic life adopted
by a large number of the members of the group; in the infested hosts they find all the
necessary conditions for their existence. Such parasites are more common in tlie in-
testine than in any other organ, but they attack every jiart of the body. In the fol-
lowing pages the habitats are considered with no little detail, so that we need not
occupy ourselves longer with the general subject.

The worms fall naturally into a number of distinct classes, some of which com-
prise but a single genus, while others are large groups and present a multitude of
forms. The jEchinorhi/nchus is so isolated among living worms that usually it is
placed from anatomical reasons by itself ; the jointed worms or annelids, on the con-
trary, have more representations in the earth's present fauna than the majority of
classes among animals. Yet these two classes are regarded by most zoologists as
peers, notwithstanding the disparity of numbers between them, because the anatomy
of the Eclihiorhynchus entitles it to as distinct a rank as is given to the annelids col-
lectively. The reader therefore must not wonder at the inequality in size of the
co-ordinate divisions of worms.

The classification here adopted is that which appears to me to best accord with
our present knowledge of the animals concerned. All the forms are bound together
by a hypothetical link, the Trochozoon, which is also the starting point of the Mol-
lusca and all bilaterally symmetrical animals. This Trochozoon must have been simi-
lar in organization to those little ci'catures, the wheel animalcules or Rotifera, and in
the course of their metamorphoses the young of many worms and anneli<ls paSvS
through what is known as the Trochozoon or Trochophora stage, so that the life his-
tory of the individual ])roves that the adult is derived by modification of the Trocho-
zoon type ; hence the induction is jirobalile that the ancestors of these animals were
Trochozoa. This necessitates placing the hypothetical animal at the base of the
system. It is, however, still questionable whether the low tyi)es known as the Plathel-
minthia, that is the tajie-worms and their allies, are not derived from something still
simpler than the Trochozoon ; the doubt as to the affinities of this class renders it
desirable to isolate it somewhat, as is done in the adjoining diagram. The rotifers
come very near the ancestral forms. Xext we jilace a very simjilj- organized small
gi'oup, the Gastrotricha, by way of which we pass off from the main line of progress
to the nematodes, to Gordius and 3f:rmis. The parasitic Echinorhynchi are usually
associated with the nematodes rather than with any other group by systematists, but
their true affinities are by no means definitely settled. Keeping on we come to the
Sagitta, and the cognate Chretosoma and Desmoscole.v. Returning now to the main
line we approach the anuelidau type. Here Ave must put first the nemertean or pro-

WORMS.

187

boscis worms, a group which, entirely without justification, was formerly included
with the jjlathelmiuths. Now intervene the Gepliyreaus. Finally we reach the
annelidan type, beginning with the Carchiannelides and leading off to the Chfetopods
and Myzostoma, the Echiurids and Balanoglossits, and to the Discophori.

Polycbjeta.

(Ecbiui'iU;i'.)'

Oligochajta
(Myzostoma.)

(Balauoglossus.j
Discophori.

Chaetosoma. Mermis.

Desmoscolex. ^ Nematod.

Sagitta.

(Ecliinoderes.)
Gastrotriclia

Hypotlaetical Protoheluiiuth.

Fig. 163. — Diagram o£ tlie natur.al afflnities of worms. The exact relationship of those forms which
are enclosed in parentheses is doubtful.

Class I. — PLATHELMINTHIA.

In fresh and salt waters, and even on moist earth, are found the free living species;
in nearly every animal are found some of the parasitic species of this huge and varied
class of worms. The members of the group offer but little resemblance with one
another as regards their external form ; one would not be led liy their appearance to
place a planarian, a fluke, and a tape-worm in the same natural division, but the inter-
nal organization of them all most clearly demonstrates the closeness of their natural
affinities. A great difference in the ways of life is con-esponded to by an equal dif-
ference anatomically. On the one hand are the non-parasitic forms, roughly called
the planarians, which require, and therefore have, well-developed organs of sense,
good means of defence against attacking enemies, perfected means of locomotion, all
the paraphernalia of independent existence ; on the other hand are the parasites,

188 LOWER INVERTEBRATES.

wliicli, being coiicealecl in the body of tlieir host, require little more than the appara-
tus for eating the victims that are also their dwellings, where they are well protected
from external attack. Parasites are always degraded in structure. Within the
present class we find a series of forms, beginning with those leading a free life and
ending with those which are parasitic during their whole existence ; with also inter-
mediate links between the extremes, species that are parasitic through a longer or
shorter term. In this series we find a progressive degradation, as the parasitism
increases until it becomes the comjjlete master of the worm's whole life. The free
living forms are the unaltered types, the undegenerated patterns of the class, of which
the parasites are the marred copies. Let us begin with the type, the planarians, or
so-called Turbellaria.

Sub-Class I. — Turbellaria.

Order I. — DENDROCCELA.

If we scoop up some mud and plants from the bottom of a ditch in which the water
is tolerably clear, and let the collected mire settle in a basin of water, maiiy strange
and interesting animals will be discovered, — many insect larva, molluscs, Crustacea,
and worms. Among them, one usually discerns some short, very dark creatures, long
in shape, quite broad and thin, which crawl about slowly, but almost incessantly, over
the sides of the basin and the' various objects in it, or indeed sometimes along the
upper surface of the water itself; their soft, flexible bodies are highly contractile, so
that the animal has hardly any definite shape, except indeed when crawling straight
forward ; for while thus progressing it always assumes a constant and characteristic
form, as shown. These worms belong to the genus Pldnaria, and are typical turbel-
larians. Of the genus several species have been described, but it is difficult to deter-
mine the specific characteristics of a Planaria. The best known and most common
form is the P. torva, found in P:urope as well as America. The planarians do not
have any means of locomotion visible to the naked eye, yet a close examination will
disclose the existence of their motor organs, for it is i)Ossible to distinguish the pass-
ino- and whirling of suspended particles in the water. These whirls are most charac-
teristic ; the very name of Turbellaria refers to them ; they are produced by immense
numbers of vibratile hairs or cilia which cover the body, especially on the ventral
side. Even in proportion to the small size of the worm the cilia are tiny,
but the united propulsions of the multitude of cilia are sufiicient to achieve
the worm's locomotion. The planarians, after the excitement produced
by their transference has ended, subside into the inanimate sediment, amidst
which they are well concealed by their dark brown color. At night time
they are more active, for it is then that they gratify their carnivorous
^'"ph^rut voracity, but they seem to me very uninteresting, except from an ana-
tomical standpoint.
In tlie same basin we may find, beside the black jdanarians, many other allied
worms, the largest among which will probably be the whitish Bendroctelam lacteum.
Some individuals measure over three-quarters of an inch in length. Its natural
habitat is on the under-side of stones and leaves. It is white, with a shimmer of gray,
and so translucent that the digestive canal shines through, and as it is usually gorged
with dark-colored food it appears very distini'tly. It is not a simple but a branched

WORMS.

189

Fig. 165. — /'<)/(/
celts tcBviffata.
a, eyes.

tube; there is a main central slL'iii runninij through the front lialf of the body, and
afiving off many lateral ramifications ; at the middle of the body the main stem forks,
producing two branches, which run backwards, and give off many secondary branches.
Where the tljree main stems unite, springs off the long, muscular proboscis, which is
an extensive cylinder for seizing and swallowing food. The prolioscis will swallow
everything small enough; in fact, its deglutive projiensities pei'sist even
o after the death of the worm ; for, sometimes, when anatomical research

J'\ has destroyed all the tissues of the creature, the proboscis, being much
•i'r. .:'?■ tougher than the rest, still remains intact, and goes on swallowing every-
thing it can seize, as if frenzied by hunger.

There are many planarians liaving a branched digestive tract, and
they ai-e all classed together, under the common appellation of Dendro-
coela, in opposition to the remaining TurbcUaria, which have a simple
straight tract, and are therefore called RhabdoccEla. It has been as-
serted by some writers that there are other species with no digestive
canal, for which the term Acoela has been proposed. It seems, how-
ever, more probable that the authors alluded to have been careless in
their observations and hasty in tlieir conclusions than that there are
any planarians really lacking a digestive tract.

Of the Dendroccela, one of the commonest is Poh/celis Icmigata, of
which we give a good figure, borrowed from Dr. Schmidt's great work
on the natural history
of the lower animals.
Of the Dendroccela, besides the
three species already mentioned, the
naturalist distinguislies many others.
A few are found in moist earth, a
goodly number in fresh water, bnt the
majority are marine. The marine
forms differ, for the most part con-
siderably, from the geneva above de-
scribed. The reproductive organs,
which are quite complicated in all
Plathelminths, are especially different.
The body is generally very broad and
thin, often translucent and beautifully
colored. In some cases a large size, a
length of several inches, is attained.
By way of illustration, we can men-
tion only a single very beautiful form,
very common in the Bay of Naples.
The animal ( Thysanozoon) may grow-
to nearly an inch in length. The back
is covered with many rows of dark
colored papillse. On the head end is
a pair of ear-shaped outgrowths, which
project obliquely ujnvards, and a]ipear to act as tentacles, with a most sensitive touch.
The ventral surface is pure white. The artist has represented the animal clinging

?

^

Fig. 166. — Thi/tiauozoon.

190

LOWER INVERTEBRATES.

to a sea-weed, with the anterior end of the Iwdy raised as if in search of a new sup-
port. The genera occurring in America have hardly been studied yet. Let us hope
that this gap in our knowledge of the American fauna will soon be filled.

The land jilanarians were first discovered by the celebrated Danish zoologist, Otto
Friederich MUllcr, in moist earth under stones. A very few species have been found
in Europe, Init none as yet, to my knowledge, in the United States; but in South
America Charles Darwin found numerous species inhabiting the moist earth of the
primitive foi'ests, where they attain a truly tro}>ical luxuriance of size and color.

Fig. KT.—A/esns-
tomum ehreu-
herpi; fi, gang-
lion; 7«,moutn.

Okder II. — RHABDOCCELA.

The Rhabdocoela are planarians built on a smaller scale and simpler pattern. Some
of them are sure to be found together with the true planarians in our ditches.
There arc two forms which I have found most abundantly in New England. The
larger one, whicli I take to be identical with Mesostomum ehrenbergi, is
a third of an inch or more long. It is whitish and translucent, and has
a broad, dark streak in the middle of the body, an effect produced by
the dark contents of the stomach, whicli the Mesostomum always keeps
well filled as long as it can secure food. If one of these worms be kept
in filtered or distilled water it finds nothing to eat, and the stomach
is gradually emptied, and the worm apjicars of the same translucent
white thi-oughout. This species is admirably adapted to anatomical in-
vestigation because its transparency reveals all its intern.al organs. The
two eye-specks are very conspicuous in front ; the mouth is near the
middle of the ventral surface, and is armed with a long proboscis;
the stomach, as in all the Rhabdocnela, is a simple wide sac without
branches. In summer time one can often distinguish several dark-brown,
small spheres on each side of the body. These are the eggs, or more cor-
rectly the egg-capsules, which are deposited on aquatic plants. In reality each capsule
contains several true eggs, which are very soft and delicate, and a certain quantity of
nutritive material deposited around the eggs, to be gradually absorbed by the latter, and
used as raw material to build np the structure of the embi-yo. The interesting manner
by which the Mesostotnum preys on Dap/mias and Cyprids is thus described by Oskar
Schmidt : — "It captures them as one might capture a fly with the hand, for it closes
the hind extremity against the front, and by bending over the edges of the body forms
a complete cavity; at first its cajiturcd prey rushes madly about, but soon the Mesos-
tomum succeeds in fastening its powerful proboscis npon its prisoner. The struggles
of the Daphni'a gradually cease; its vampyre then stretches itself, and crawls away,
having sucked the life-blood of its victim."

The second species is very common, be'ng often found npon the well-known
aquatic plant Utricularia. It measures scarcely an eighth of an inch in length, and
is remarkable for its bright green color, so uncommon among animals ; its anterior
end is somewhat pointed or conical. This I believe to be the l^ortex viridis of
European naturalists. It is remarkable for its gregarious habits, large numbers being
found together.

Although there arc many genera and more species of this group known to natural-
ists, both from fresh and salt water, there is little in their habits to awaken general
interest. We will therefore close our account by a brief mention of the genus Con-

WORMS. 191

valuta, which comprises small worms which have the thin lateral portions of their
bodies curled over on to the ventral side.

In connection with the Rhabdocwla we may refer to a small aberrant group of
worms, the ^Irrostomid^, although they differ in two respects very strikingly from
the true Turbcllaria. They are mainly not hermaphrodite, and multiply not only by
ova but also asexually by spontaneous division, like many annelids (Nais, Auto-
lytus, etc.).

Sub-Class II. — Trematoda.

The large class of animals to which we now turn our attention offers some of the
most interesting life-histories known. The flukes or Trematoda are all parasitic upon
other animals, and accomplish during their lives strange migrations and metamorphoses.
According to their stage of development varies their habitat ; usually the embryo
swims about for a short time in the water ; it then becomes a parasite by entering the
body of its first host, where it changes its form, and by a singular process of asexual
propagation it becomes the parent of several or many individuals belonging to a second
generation. The members of the second generation in some cases multiply further,
and the descendants mature to the final sexual stage, Avhile in other instances they
change directly into the adult form. In those species which pursue the more complex
metamorphoses, the parasite may in successive stages infest as many as three different
hosts. In general the adult fluke does not live in a host of the same species as the
larval worm.

We cannot better gather a notion of the characteristics of the trematode worms
than by following the history of one species as a concrete example of the habits of the
class. For this purpose we choose the liver fluke, Distoiumn /lepaticum. The adult
worm infests the liver of mammals. It is an hermaphrodite, and every worm produces
several hundreds of tliousands of small eggs, which it discharges into the bile ducts.
The eggs then pass into the intestines, and out with the droppings of the host, in
which they may bo found abundantly. The cmln-yo is devclojied within the egg shell,
and when mature bursts open the little cap or operculum ; this occurs only when the
egg is supplied with moisture. If it falls or is washed intt> some pool the embi-yo
survives its birth, and immediately begins swimming freely in the water.
Its form is an elongated cone, Fig. 108, with rounded apex, and measur-
ing 0.13 mm. in length. The base of the cone is directed forwards, and
in its centre is a short, retractile head pajiilla. The whole surface is
covered by cilia, springing from large cells, which form the external en-
velope or so-called ectoderm of the embryo. In the interior are two
eyes, and other structures, which we will not pause to describe. The
embryo is exceedingly active, swimming about like an infusorian, though
more rapidly. Now in England, where this worm has been most suc-
cessfully studied, there lives in the ponds and ditches of the fields a
snail known to zoologists by the name of Lymncexis trunculatus. When
the larval Distomum in the course of its gyrations happens to meet one , Fi"- les.— Fit-e-

a 1 p .1 . , . ^ rr,, . , swimming em-

01 these unfortunate snads it attacks it. The worm presses its head- biyo of Dis-
papilla against the surface of the snail, and begins spinning like a top
around its own axis, and working its body until the tissues of the snail are forced apart,
leaving a gap through which the embryo squeezes its way into its host. The embryo

192

LOWER IN VER TEBRA TES.

Fig. 169. — Cyst
of Distoma.

J

appears to have sonic means of instinctively recognizing the irunculatus, for it does
not attack other species of snails. It cannot live nuich more than twelve hours in
water, and it usually gets into a snail within eight hours. In its host the embryo
clianges into a new form, the nurse or sporocyst, within which arise the
germs or spores producing new individuals. The outer ciliated cells
swell up, and are finally cast off. The embryo then becomes a little
bag or cyst, at one end of which the pigmented eye-spots of the embryo
can still be recognized. The cyst or nurse grows and elongates. During
warm summer weather it may reach its full size within a fortnight, but
in autumn twice that time may be necessary. These cysts sometimes,
but rarely, multiply by transverse division, but in other species this
phenomenon is more frequent.

The next larval forms, the rediae, are developed within the sporocyst. The first
clearly recognized appearance of the redia; is a mulberry-like cluster of cells, over
which a structureless membrane is soon formed, while the pharynx and
other organs of the redia are produced in the cluster. There are
usually several of these germs in each cyst. This is a verj' character-
istic stage in the life history of the Trcmatoda ; the embryo is converted
into a bag, in which the germs of a new generation of individuals
originate and are confined until far advanced in their development;
the body of the parent is converted into a temporary prison-house for
the progeny. The sporocysts of one species or another may be found
in nearly every snail ; many kinds are bizarre in shajie, and all offer
the curious spectacle of the living germs squirming about and nearly
filling the whole of the cyst, their common parent. In the cysts of
Dislomiim hepatinim, there is usually one redia, less frequently two,
nearly ready to leave the sporocyst, with two or three germs of medium
size, and several small ones. When ready to leave the sporocyst, the
redia by its own motion makes a forcible exit l)y rupturing the walls
confining it. The free rediie force their way through the tissues of
the host, and are found especially in the liver. They
increase in length, to 1.3 mm. or 1.6 mm. ; a sort
of collar is formed meanwhile a little behind the
jiharynx. In other respects, except that they have a
digestive tract, which is wanting in the cysts, the
rediic resemble the sporocysts in structure ; their most
important new feature is the I)irth opening at the side
of the body just behind the collar, which permits the
exit of the new brood developed within the redia.
The germs develop similarly to those of the sporo-
cysts, but are more niunerous. Sometimes they pro-
duce a second generation of rediae, probably as long as the weather
continues warm, but sooner or later, usually when cooler autumn
weather begins, there come rediae, which produce a new stage, the
cercaria, in the series of metamorphoses. The cercaria is the typical
larval fluke, and is easily recognized from its .appearance, which re-
minds one of a tadpole, as is shown in Fig. 171 ; it has a large body nearly as broad
as long, and flattened, with a long round tail. In the interior of the body one can

Fig. 170. — Kedia
of Dlstoma.

Fig. 171. — Cercaria
of Disfoma,

WORMS.

193

Fio. 172. — Cys-
togeuous cells.

distinguish portions of the digestive tract and numerous cells, three of which with
tlieir granular contents are represented very much magnified in Fig. ll'I. These cells
have a glandular character and serve to pour out a mucous secretion, the
function of which will be immediately described. There may be as
many as twenty-three spores in various stages of development in one
redia; out of these spores there will be one, two, or three cercariai
approaching complete develo])ment.

As soon us the cercaria has reached the limit of its development
within the redia, it escapes from the parent by the birth opening. When free, the
cercaria, Fig. 171, is very active, aiul constantly changes its form. By tlie aid of its
suckers, the tadi:)ole-sha])ed larva crawls or wriggles its way out of its host. When the
infested cells are kept in an aquarium, the cercaria; may be found occasKjnally swim-
miini" about in the water ; but not long, for on coming in contact with the side of the
aquarium or willi water-plants, it proceeds to encyst itself. The process can be readily
observed under the microscope ; for, on a glass slide, the cercaria soon comes to rest.
It assumes a rounded form, whilst a mucous substance is poured forth over the body
together with the granules of the cystogenous cells, which we mentioned above. The
tail is shaken off either befoi-e or during encystation, which is com-
pleted in a few minutes. These cysts are the means of infecting the
final vertebrate host of the parasites, the infection being rendered
possible by the habits of the intermediate host, liinmceus trimcattdus,
which might well be termed amphibious, so strongly is its habit of
wandering on land developed. Indeed they can remain on land for
long periods, and resist even prolonged droughts : hence when in the
water, tlie snails become infested, and wlieu on laud, leave the cer-
cariaB that crawl out of tlieir first host scattered over the fields, wliere
they encyst on the grass and are eaten by the sheep and other animals.
In the stomach of the unlucky sheep the cyst is dissolved, leaving
the worm free. The worm then makes its way into the liver, and
probably in about six weeks begins to ])roduce eggs, growing itself
meanwhile. During its growth its external form changes, the simple
forked intestine develops numerous blind secondary
branches, the posterior sucker is greatly enlarged and the sexual
oi'gans are matured. Thereafter the wondrous cycle of metamor-
phoses and emigration recommences with the new eggs. There are,
perhaps, no instances more striking of the adaptation of animal species
to ])artieular conditions of existence than we encounter in the life
histories of trematode worms, one of which we have narrated.

The adult worm, Distomiim /lejKtticicm, attains a length of three-
quarters of an indi ; it is broad and flat and at its anterior end has a
small projecting lobe, which bears two ventral suckers, one in front
at the very extremity surrounds the mouth, the second one consider-
ably larger lies an eiglith of an inch or more further back. It is found
in nu)st ruminants and in many other animals including man ; it is
commonly encountered in the biliary ducts, but is sometimes found
in the intestine or venous system. Geographically it is very widely
distributed not only throughout Europe and America, but also in Egyj)!, India, and even
Australia and Van Diemen's Land. Although discovered by Gabucinus as long ago as

VOL. I. — 13

FjG. 173.— Youiig
Jilsfomum : Ij,
lih;irviix; c, sto-
mach; <», uiaulh;
s, sueliers.

Flo. 174. — DittUniiuiit
fft'paticwn, liver
Hake.

1131

LOWER INVERTEBRATES.

llie middle of the sixteenth century, it was not until 1882 tliut the complete Hie history
was known, as we related above. They are very injurious to their hosts on account of
the interference with the discharge of bile, which easily becomes serious and even fatal
to their unfortunate entertainer.

The genus iJistomuDi is a very extensive one, coui)irising a great many species, in-
festing au almost incredible variety of animals; indeed, it may be questioned if there
is any other genus of living things privileged to be such a universal infliction. Man
alone is exposed to the attacks of no less than five different species, while the poor frog
is even more numerously endangered. Molluscs suffer especially from the attacks of
the Distonmm in its larval state, so that it is not at all uncommon to find the Avhole body,
of a pond-snail for example, crowded with sporocysts or rediie. The following ai'e the
species which attack man: Dlstomum crassMw*, occurring in China — it inhabits the
intestine and grows to one or two inches in length ; D. laaceolatam, which occurs to-
gether with the true river fluke, but is nmch shorter, and, proportionally, much narrower,
so that it can be very readily distinguished from the hqmticiiiii ; next a doubtful
species which has been only once observed, JJ. opthalmubituu ; and, finally, the 2>.
heterophyes, known only in Egypt. The genus may be readily recognized by the two
ventral suckers, which lie near together at the anterior end of the body.

The Trematoda are divided into two
orders, the Distomeaj and Polystomeae.
The former comprises those forms that are
related to the genus Distornum, and have
two or sometimes only one sucker, while the
latter have two lateral small suckers at the
anterior end of tlie body and one or several
suckers posteriorly, while connected with
the latter are often several hooklcts. In
the first order there reigns a considerable
similarity of appearance, Avhile in the sec-
ond there is an unusual degree of diversity.
Among the Polystome;e, howevei', is one S])e-
cies which offers the wondering naturalist
an unparalleled phenomena- — two separate
and comjilete individuals united in one.

The Diplozoon paradoxum, to which
the closing sentence of the previous para-
graph referred, is indeed well named, for
it is literally two animals united in one.
There are two bodies precisely resembling
each other in every particular, and united,
like the Siamese twins, by a narrow communicating band, so as to form but one ani-
mal, the nutrient canals of one division communicating freely with those of the oppo-
site half. One might easily regard this extraordinary arrangement as an accidental mon-
strosity, but observation has jiroved it to be common to all the individuals of the
species. The animals, which are of very small size, being not more than tv\o or three
lines in length, ai-e found attached to the gills of the bream, from which they derive
nutriment. Siebold discovered that the Diplozooii arises by the union of two distinct
worms, and the whole life history was subsequently worked out with great exactitude

Fig. 175. — Dlplozoon paradoxHin ,' a, mouth; b, ante-
rior suckers; c, stoiuaeli: /, oviducts; ;/, uterus; (.,
testis; A:, vns deferens; //vascular cailals; 7h, pos-
terior suckers.

WORMS.

195

I'lG. 176. — Vip-
orpa.

Fig. 177. — Egg of Dlplozoon.

by Zeller. The larva was formerly sui)iiosed to be a distinct creature, and went by tlie
name of Diporpa, Fig. 176. The Diplozooti is the mature sexual form, which produces
the eggs, long oval capsules, with a long snarled thread running off from
one end. The egg, P^ig. 177, breaks ojjen, .and the larva swims about in
search of its host, to which, when found, it attaches itself upon the gills,
living there, in company with the adult, perhajjs
for months, but after a while they pair off ; there
is a little knob on the back of eacli Diporpa, and,
of course, a ventral sucker; when two join they
twist over so that each seizes with its sucker the
dorsal knob of the other, and so they remain,
and in due time actually grow together. They
are, in truth, the most monogamous of animals,
for each individual can have one mate only, from
whom he can never be divorced. The union takes
jilace in such wise that the animals form a cross.
The left tail belongs to the right head. Each member of the
Diplozoon has nine suckers, tWo in front, by the mouth, one
near the middle, and six at the posterior extremity of the body.
Dr. Ernst Zeller has worked out very carefully the complicated history of a typical
species of the second group of trematods, namely, the Polystomum integervbniaii^
parasitic in the bladder of frogs. The animal grows to a third of an inch in length,
and is remarkable for having, unlike most Trematoda, a branching intestine; the
posterior end of its body is expanded into a broad disc, with three pairs of suck-
ers on its under side. The eggs are dischai-ged by the parent in the bladder, and ex-
pelled into the water. The larva hatches out in from fourteen to forty days, accord-
ing to the temperature. "The young worm," writes Dr. Zeller, "is an extremely
lively, active animal, and swims about merrily in the water Ijy means of its coat of
cilia; contracting and stretching its body, bending and turning, and often, also, bend-
ing its head down, turns a somersault as quick as a flash." Under ordinaiy conditions
the eggs are laid in the spring, when the frogs awake from hibernation, and the lar\-a3
are hatched at a period when the tadpoles are in a somewhat advanced stage of evolu-
tion. From the water the active larviB get into the branchial chambers of
the tadpoles, where they take their abode for about two months ; when
the gills of the frog begin to disappear they migrate through the oeso-
phagus and intestine to the bladder, and in three years attain sexual
maturity. On the other hand, when the formation of the eggs and the
evolution of the Polystomum. larvaj are artificially accelerated by keep-
ing the frogs in heated rooms, the larvse are hatched at a period when
the tadpoles are quite young and their gills very delicate. Their evolu-
tion is then very rapid. They become mature and produce eggs within
five weeks; their life is at an end before the gills of their hosts are
obliterated, and they never migrate into its internal organs. The
remarkable conclusion of the varying life-history is a difference in the
adult, for the gill-cavity Polystoma are very unlike the normal adults
in form, app^ai-ance, and their whole .anatomy. Extern.al circumstances
here produce a maximum effect, for when they are changed in a certain manner the
same eggs which would nominally iwoduce the ordinary Pohjstornurn integerrimimi

Vh\. 178. — Young
of Polystomum.

196

LOWER INVERTEBRATES.

develop into a parasite, which, were its history not known, v/ouki not be supposed to
have any connection with the species to which it really belongs.

The Polystoraeaj include a great variety of strangx'ly-shaped parasites, the major-
ity of which infest fishes. Especially remarkable nre the marine forms, many of which
have been described by the elder Van Beneden, and illustrated by a series of beauti-
ful plates, which record the bizarre outlines and colors of many species. Little, how-
ever, is yet known concerning the history of most of these trematods.

The following paragraphs, for which I am indebted to my able friend, Dr. C. O.
Whitman, refer to a group of worms, the Dicyemidw, which he has studied more ]iro-
foundly than any other zoologist. Although their systematic position is doubtfid, it
seems to me most probable that they are larval trematods.

The DiCYEMiD.E are parasitic worms inhabiting the renal oi-gan of the cuttle-fish,
the poulji, and other cephalopods. Only ten species have thus far been described, and
these, with one exception, belong to the fauna of the Mediterranean. These creatures

are attached to the renal organ by the head, the body
floating free in the fluid that fills the sack enclosing
the renal organ. The different species vary in length
from 1 to 7 mm., and all have the same habits and
life history. The entire renal organ is often beset
by these animals, which, to the naked eye, appears
as shoi't, white, undulating hairs. They have no
mouth, no stomach, no muscle, no nerve, nor organ
of any kind. The entire animal is made up of a few
cells varying, according to the species, from twenty
to thirty. There is one long axial cell (Fig. 179,
en) stretching through the entire length of the para-
site ; the remaining cells form an envelope (cc) for
the axial cell. The cells of the epithelial envelope
are arranged in a single layer, and clothed with vib-
ratile cilia. At the anterior fixed end, a certain
number of these cells, which are elsewhere elongated
and thin, are short and thick, and more closely cili-
ated, thus forming what may be called a head. The
number, arrangement, and shape of the head cells,
furnish, according to Whitman, the chief generic
and specific distinctions. Seven species have each
eight head cells, disposed in two sets, four propolar
(cq)), and four metnpolar (»y5), and thus form a generic group, to which the name
Dicyema has been given (Fig. 179, A). The three remaining species have each nine
head cells (Fig. 179, B), four propolars («/>), and five metnpolars (w>/'), and have there-
fore received the generic name Dicyemennea.

The structural simplicity of these animals is most probably due to degeneration
resulting from their parasitic mode of life. "When we find an animrd in the form of
a sim]ile sack, filled with reproductive elements, secured by position against enemies,
sujiplied with food in abundance, and combining parasitism with immobility, we have
strong reasons for believing that the simplicity of its structure is more or less the
result of the luxurious conditions of life which it enjoys, even if its development fur-
nishes no positive evidence of degeneration." Physiologically speaking, the axial ccU

Fig. 170. — A, Dicj/cma. 15, Dicyememiea;
ap, propolar ceilp; e, embryo; en^ axial
cell; ec. outer cell; 7>*;?, metapolar cells;
n, nucleus.

WORMS.

197

t'lG. l.SO. —Development of the vermiform enibrj'o
of jyicyema; tu, axial cell; (i, germ cell; n,
nucleus.

is a uterus ; for in it the germ cells, or ova, are lodged, and it is here that all the known
stages of develoisment are completed. The fully-formed embryos escape from the
pai'ent by pushing their way out between the cells of the epithelial envelope.

The reproductive cycle of these worms has not yet been fully ascertained; but
some verv interesting pnrlicins of it have been made known by the investigations of

Van Beneden and Wliitman. As Kolliker first
j)ointed out, the Dicyemids produce two very
distinct kinds of embryos, which he distin-
guislied by the terms vermiform and infusori-
fonn. The vermiform embiyo (Fig. 180, F)
develops directly into the parent form without
metamorphos's. The fate of the infusoriform
embryo (Fig. 181) still remains a puzzle; but
it may be safely assumed that it either repre-
sents a male individual or a special form which serves to carry the species to new
hosts. In the latter case, as suggested by Balfour, it is not improbable that in the
course of a free existence, it may develoj) into a sexual form, the jDrogeny of which
are destined to complete the cycle of development by
becoming again parasitic in the renal organ of a cepha-
lopod.

Fig. 180, A to ¥, represents the more iinportant
phases in the development of the vermiform embryo.
From the germ cell (A) arises, by division, a two-cell
stage (B), then a four-cell stnge. One of the four cells
(en) now remains passive, while the other three go on
dividing (C,.D), and arrange themselves so as eventually to completely inclose the
passive cell (E), which thus becomes the axial cell. Tlie axial cell elongates as it
becomes enclosed, and from its two ends two cells {(/) are split off at an early date,
which give rise by division to the germ cells. The embryo (F) attains nearly the
adult form, and is clothed with cilia before escaping from the parent.

The infusoriform embryo, seen in Fig. 181, is somewhat jiyriform, with the broader
end directed forward in swimming. It has a complicated structure, the significance
of which is entirely unknown. At the anterior end are seen two refractive bodies (?•)
wliich lie above an organ called the urn (n). The urn consists of a wall (ii), and a
lid (/), and contains four polynuclear cells igr). The wall of the urn is hemispherical,
and composed of two halves. The lid is made up of four cells.

The cells that form the posterior extreinity of the embryo are ciliated. The germ
cells that give rise to the infusoriform embryos are larger and much less numerous
than those which develo]> into vermiform embryos.

As the two kinds of embryos are never found simultaneously in the same parent
form, it has been supposed that there are two distinct adult forms, one of which pro-
duces exclusively vermiform embryos, the others exclusively infusoriform embryos.
The former have been called Nematogens, the latter Rhombogens. It has now been
ascertained that this distinction is not valid, the two forms being only two phases in
the same individual cycle of life. There appears to be two kinds of Dicyemids, how-
ever, one of which, so far as known, produce only vermiform embryos, the other pro-
duces first infusoriform embryos, and subsequently, after the escape of all these
embryos, vermiform embryos.

Fig. ISl. — lufusonform emliijo

198 LOWER INVERTEBRATES.

Considerable difference of opinion exists in regard to the systematic position of tlie
dicyemids, some contending that they form an independent group, intermediate
between the Protozoa and the higher animals, others, that they represent a degenerate
branch of some division of the worms, perhaps of trematods.

Sub-Class III. — Cestoda.

The tape-worms or cestods are among the most dreaded enemies of mankind, and
they inllict terrible destruction upon nearly all vertebrates, especially uj30n carnivorous
species. A tape-worm is an elongated animal, usually so broad and thin as to suggest a
ribbon or tajje ; one end is thickened and represents the head, having an imperfect or
rudimentary brain, but lacking entirely organs of special sense, although possessing
some specialized organs, hooks and suckers by which the woinn anchors itself in the
tissues of its unfortunate host. The long body is either a continuous band or else is
divided up into parts called proglottids, forming a longer or shorter chain as the case
may be. They have no trace of any digestive canal, but on the contrary have lost
even that by the degeneration consequent upon their exclusively parasitic life ; ajipar-
ently their nutrition is effected by the absorption of the juices of the host through the
skin of the jjarasites.

It is not diificult to trace out a series of genera by which one can pass gradually
from the trematode type to the extreme of the cestode type, for there are certain
flukes which approximate to the simpler tape-worms. In the genus Cari/ophi/llceus
we have in fact a tape-worm, which might well be described as a fluke that had lost
its digestive tract by excessive degeneration. In Ligula the body is partially divided
up, while in Tctnia it is completely jointed, each joint or proglottis having its full set
of reproductive organs. Tmnia is in fact the extreme product of the changes which
have occurred in the parasitic Plathelminths, and as it is also one of the best known
as well as most feared of the whole class, we will consider their life liistory first. At
least seven species of Tcenia attack man ; but of tliese only three are frequent, namely,
T. solium, T. mediocanneUata, and T. echinococcns. They all inhabit the intestines,
where they burrow their heads into the walls. The two species named fii-st grow to a
very large size, solium reaching sometimes a length of three yards, mediocannellata a
length of four yards, while echinococcus does not exceed four millimeters, scarce one
one-hundredth of the length of mediocannellata.

The Tcenia solium has a small head, about the size of that of a pin, within a long,
thin neck, which gradually widens until the body is some six or seven millimeters
broad. The whole body behind the head is divided up into proglottids or joints,
which are so fine in the region of the neck as to be undistinguishable by the naked
eye, but a couple of inches further back the narrow joints are plainly visible ; the
further down, the longer and larger the joints become. In each joint a set of eggs is
formed, and in the last proglottid the eggs are mature ; the last joint falls off and is
discharged with the egesta ; the new last joint, previously the penultimate, ripens and
falls off in its turn*; now the new joints are formed in front just behind the head, and
each new joint as it shoves the others back acquires its place in the series, to be in its
turn shoved back by fresh joints ; thus the process continues, how long is not exactly
known, but at least until hundreds of joints, each crowded with eggs, have been sepa-
rated from the ]iarent band. The head is remnrkalile for its armature; upon the crown
is a circle of some six and twenty hooks, and four suckers arm the sides of the head.

WOIiMS. 199

The hooks, as seen under the raioroscope, form a regular circle, alternately big and
little claws. The suckers are very muscular, the fibres being arranged in two systems,
one equatorial and one meridional. Altogether the means are very
ample to secure the hold of the worm upon its abiding place.

The proglottids, after their expulsion from the body of the host,
may be compared to the sporocysts of the flukes, for the eggs develojj
into embryos within the proglottids, so that they become cysts filled
with larvEe. " The growth of the nudtitude of embryos within their
interior causes the proglottis sooner or later to burst, and the embryos F10.I82.— Hooks oi

^ ^- ^ •^ Iteitia solium.

thus become dispersed ; some are conveyed down drains and sewers,
others are lodged by the roadsides in ditches and waste places, whilst great quantities
are scattered far and wide, by winds or insects, in every conceivable direction. Each
embryo within the egg is furnished with a special boring apparatus, having at its anterior
end three pairs of hooks ; after a while, as it were by accident, some animal, a pig-
perhaps, coming in the way of these embryos, or of the proglottids, swallows some of
them along with matters taken in as food. The embryos, immediately on being trans-
ferred to the digestive canal of the pig, escape out of the egg-shells, and bore their
way through the living tissues of the animal to lodge themselves in the fatty jiarts of
the flesh, where they await tiieir further destiny. The flesh of the animal thus infested
constitutes the so-called measly pork. In this situation the embryos drop their hooks,
or boring apparatus, and become transformed into the Cysticereus cellulosa'. A por-
tion of this measled meat being eaten liy ourselves transfers the Cysticercus to our own
alimentary canal, to the walls of which the larva attaches itself" (Cobbold). The
Cysticercus is the larva wliich infests the pig. Originally no helminthologist surmised
the existence of a genetic connection between the parasites in swine and the human
tape-worms. The great German zoologist von Siebold was the first to establish tlie
exact metamorphoses, while Kuchennieister had the merit of clinching the proof Iiy
experiment.

The life history of Tcenia solium illustrates the phases as they occur in nearly all
tape-worms infesting carnivorous animals. The cestods of the herbivores have a sim-
pler history, which we will relate directly. For the moment let us consider the more
complicated type of development : The eggs or embryos are dropped about, to be
swallowed by the first host, in which they assume the first or larval form ; the host is
preyed upon by some carnivorous animal, which, together with the flesh of its victim,
swallows some of the larva^, and these then undergo their final develojmient. In order
to reach their ultimate abode the piarasite must twice be swallowed by a host ; it
accomplishes its migrations passively by the aid of the very animals it injures. The
larva is always a vesicular structure, a membranous sack with a little ajipendix, which
becomes the head of the adult worm. Imagine a glove of which the hand makes a
closed bag, and which jwssesses only a single finger ; imagine also the tip of the finger
armed with a circlet of hooks and four suckers ; finally turn the finger in so that it
forms an inverted tube extending into the hand of the glove ; thus we can conceive a
good model of a Cysticercus ; the vesicle itself is about a quarter of an inch long, and
of a pale flesh color. Ordinarily the head is found turned in, but sometimes it is
everted, and eversion always takes place after the larva enters the intestine of its
second host. Now when the head is protruded the vesicle becomes the posterior por-
tion of the body, and the proglottids being developed behind the head, the tajie-worm
is gradually formed in about three months by the continued interpolation of new joints

200

LO WER INVER TEBRA TES.

Fig. 183.

■ Tccnia echlnococcus from pig
and dog.

in front, and the steady enlargement of those once formed, until the hindmost ones,
being fully matured, drop off the chain.

Tcema mediocaniiellata is distinguished from solium by the want of hooks on the
head, and by the fapt that the broadest 2MXigluttids are those half mature at the middle
of the ribbon. The Cysticercus stage is passed in the flesh of cattle.

In T<enia echinococcus tlie history is revei'sed, and offers many extraordinary pecu-
liarities besides : reversed because the larval stage infests man and other aniuuils, while

the adult is found in one of man's domestic animals,
the dog ; peculiar chiefly because one larva i^roduces
several adults, and also because the larva differs very
mncli when found in man from its form otherwise.
The larva in the pig bears the name of echinococcus ;
it is a large round vesicle usually the size of a walnut,
but sometimes growing to be as big as an orange.
Usually it is found in the liver, sometimes in the
lungs, and even in other positions. The thin-walled
has: has several ingrowths, as shown at A in the
accompanying wood-cut, each ingrowth is an in-
vaginated head, and becomes a distinct adult indi-
vidual. These are everted and broken off, and are
found in the intestine of tlie dog shortly after it has eaten the infested flesh of a pig.
The crown of numerous small hooks around the head enables the young worm to
anchor itself. It forms only a few proglottids at a time, Fig. B, so that the adult is
not more than four millimeters long, the terminal joint soon matures, breaks off, an<l is
replaced. In man, however, the larva is still more complicated, for from the main
vesicle grow out secondary sacks, and from the walls of these latter the heads are sus-
pended ; the heads thus lie in distinct capsules outside the m;iin vesicle. The illustra-
tion, copied from Leuckart, shows the edge of the central
sack with one "Brutkapsel" ])rojecting from it. The
Icelanders are very extensively afilicted by this ]iara-
site, nnil the fact is attributed to their want of cleanli-
ness and the number of dogs that they keeji around
them. The dogs scatter about the proglottids with
their dung, leaving the eggs directly or indirectly upon
the plants which the Icelanders eat; for they gather
for food certain mosses, sorrel, dandelion, and so forth,
from the midst of the plains, in which live flocks of
sheep guarded by dogs. The vesicles are found in all
parts of the body, for when the larv£e are set free in the intestine of man they wander
about everywhere, until they finally come to rest, and change to the many-headed
vesicles. As the vesicles, or hydatids, as they are often called, enlarge, they produce
very serious disturbances, and are often fatal.

Besides the echinococcus, dogs are infested by Tcenia serrata, which lives as the
Cysticercus pisifonnis in the peritonaeum of rabbits and hares, and also by T. cucu-
merince. " Some years ago," says van Beneden the elder, " while making a post
mortem examination, at the Museum of Paris, of some young dogs which I had ])rc-
viously infected witli Tamia serrata. at Louvain, there were found by the side of these
some Tcenia ciicicmeri nee. These dogs had taken nothing but milk and Cvsticerci!

Fig. 184. — Tt^tiia echhwcoccus, a single
" Bvutliapsel," from man.

WORMS.

201

Whence came these I'cenia cucumeritice? I knew not, and I frankly owned it to
members of the commission who proposed the question to me. This, however, did
not prevent my being greatly puzzled by the presence of this worm, of whose origin I
liad no idea. Now we know whence they came. An acaris, the Trichodectes, lives in
the hair of young dogs, and harbors the scolex (larva) of this cestode. The dog, by
licking its own haii-, gi'ows infested, like the horse, which in a similar manner intro-
duces the gad-riy, and, though it has taken no other nourishment, harbors its own
epizoaria."

Sheep are afflicted by a disease known as the " gid," or " staggers." The .animal goes
round and round ; its power to walk straight ahead is lost. This curious effect is pro-
duced by the presence of a hyd.atid, a many-headed larva of a tape-worm ; the larva lias
lonii- been known under the name of Cwiiurics cerebralis, and is the cause of a mortal
disease but too well known to the farmer. The pressure and irritation caused by the
hydatid produces inflammation and degeneration in the surrounding tissues. For a
long time the further metamoi'i)hoses of this sj^ecies remained undiscovered, but it
has shice been ascertained that the mature stage is reached in the dog.

The second family of Cestodes, the Tseniadse being the first, are the Bothkiocepha-
LiD^, distinguished by having oidy two ■\\-eak and shallow suckers on the head. Both-
riocephalus latus is the largest of internal human parasites, specimens occurring
twenty-five and thirty feet in length. Its history has not yet been satisfactorily
worked out, but it is known that the eml>ryo first enters the water, and probably
passes its larva life in a fish.

We will not attempt to describe all the types which mark off the families of tape-
worms, but we can at least indicate the great variety of apjiearances among the spe-
cies. This is especially noticeable in the tape-
worms of birds and reptiles, whose predaceous
habits lead them to engulph many aquatic ani-
mals laden with larval plathelminths, which reach
their full development in the bird or lizard. The
accompanying wood-cut shows two forms. A,
Tcenia filum, which was described long ago by
Goeze ; the head is scarce over a millimeter in
width, and is furnished with a crown of ten small
hooks ; the cystieercus stage is unknown, but the
adult is found in the intestine of Hcolopax, Tot-
anus., and Trinrja. B represents the very singu-
lar Ophryocotyle 2}roteus, originally discovered by
Dr. Friis ; the head ends in a large fan-shaped
cupula, and bears six distinct festoon-like suckers ;
it grows to a length ordinarily of four inches ; it
is found in the intestine of certain sandpipers and
))lovers. There is a rich field of interesting study
open to a naturalist who will turn his attention to the parasitic plathelminths of our
water and shore birds. Another very remarkable genus has been found in Varamis, a
genus of lizards, and recently described by Prof. Perrier of Paris, and were obtained
by M. Vallee from the lizards kept at the Jardin des Plantes. The tape-worm in
question has been named DutMersia, after Prof. Lacaze-Duthiers ; it is distinguished
by the enormous development of the lateral suckers, which form two large cujis with

Fig. 185.

-A, Tcenia fihim; B, Ophrijocniijle
2)r6teus.

202

LOWER INVERTEBUATES.

crenull.ited edges ; the cups are soldered together in the median line ; a similar arrange-
ment, but on a much smaller scale, exists in Soleuuphorus^ and indeed there can be no

doubt that both the genera alluded to belong to the
family of Bothryocej)halida?.

Our herbivorous domestic animals are much infested
liy tape-worms, the horse, sheep, goat, and cattle, each
have distinct sjiecies. The horse is especially subject to
their attacks, and has three species joeculiar to itsi'lf,
namely, Tmnia iMcatu^ T. mandlluna^ and T. perfollata.
These worms sometimes occur in large numbers in a
single host ; Ghabert counted ninety-one from one horse.
It is supposed that these species have free-swimming
aquatic larv£e, which the horses swallow in drinking;
but of none of them is the history satisfactorily known.

Thus we terminate our brief account of the parasitic
platlielminths. The subject is a repulsive one, but is full
of instruction to the thoughtful naturalist. To trace out
the life histories, so bafHing to the student, has I'equired
the greatest pei-severance and acumen ; and our j^resent
knowledge is a very remarkable mouumeut to the patience
and skill of scientific naturalists.

Class 11. — ROTIFERA.

The Rotifera or wheel-animalcules are small creatures
found in marine and fresh waters, but most abundant in
stagnant pools, and often in places where water has stood
for a few weeks only. They equal a pin's head in size,
and are very transparent, so that an entire animal may
be forced to disi^lay its complicated anatomy at one view to the inquisitive micro-
scopist. They are all, except the sessile forms, agile and restless, and dart about
eagerly and rapidly, so that they are hard to follow with the eye ; but, forttmately,
they have a liking for occasional repose, and will sometimes keep delightfully still,
long enough for the keen observer to discover some
of the secrets of their organization and of their
physiological processes.

One of the most familiar forms is the little
wheel-bearer. Rotifer vulgaris, which may be col-

PiG. 186. — DiUhiersia exjxmsa.

lected during the warm season from almost every
ditch. The body of this animal, when fully ex-
tended, possesses greater length, in jiroportion to
its breadth, than most others of its class. The tail
commonly has three joints or segments which are
capable of being drawn one within the other. This
animalcule may be considered tyjiical of its class.
There are no legs ; the antei-ior portion of the body
is furnished with a retractile lobed disc, of which the margin is covered \\\X\\ vibratile
cilia, while at the opposite end of the body is a cylindrical process forked at its ex-

Fjg. 1S7

-jNIastax of Eachlanh

WORMS.

203

tremity. This false foot or tail is jointed, and can be contracted and extended like a
telescope. It does not form a direct prolongation of the end of the body, but arises
from and is situated upon the ventral aspect. In most wheel animalcules there are
two eye specks, which are \isually reddish in color. The cesophagus is provided with
a complicated masticating apparatus, the so-called " niastax," which is very interestino-
to the anatomist. Such are the general characteristics of the grouja.

The class was formerly confounded with the chaotic assemblage of minute
creatures, to which the name of infusorial animalcules was applied rather for conve-
nience than from discrimination ; but, says Ryuier Jones, " the information at present
in our possession concerning their internal structure and general economv, while it
exhibits, in a striking manner, the assiduity of
modern observers and the perfection of our
means of exploring microscopic objects, en-
ables us satisfactorily to define the limits of
this interesting group of beings, and assign to
them the elevated rank in the scale of zoologi-
cal classification to which, from their superior
organization, they are entitled." The ciliated
lobes at the anterior end of the body have
given the class its name ; yet there are forms
known in which the cilia are wanting and the
lobes are excessively modified in shape. This
is notably the case in the parasitic genera Al-
bertia, JJakitro, Seisoi), etc., which form the
family of the Ateocha (wheelless), and also in
certain species not parasitic. Of the latter, the
best known is a rotifer, described in 1857 by
the distinguished veteran among zoological in-
vestigators, Professor Leidy of Philadelphia,
under the name of Dictyophoru vorax. This
rotifer is now united with several other allied
species in one genus, Apsilus. Apsilus vorcne
is spheroidal, has no jointed tail, but is sessile.
Instead of the ordinary rotary discs it pos-
sesses a large protractile cup or disc. The
animal has the power of turning upon its point
of attachment, but does not ap))ear to have the
power of letting go its hold. The animal is about one twenty-fifth of an inch long; in
shape ovoid, the narrower polo being truncated and bearing the mouth. The body is
transparent, colorless, and even, and exhibits no signs of annulation, nor does it become
transversely wrinkled by contraction. The interior exhibits the digestive apparatus
and other organs, mostly more or less obscured by an accumulation of eggs in various
stages of development. From the truncated extremity of the body, the animal pro-
jects a delicate membranous cup, forming more than half a s]:)here and more than half
the size of the body. At will the cup is entirely withdrawn into the body, but, when
protruded, ex]iands outwardly like an opening umbrella, and is the substitute for the
ordinary trochal discs of rotifers, and appears a most efficient means in catching the
animalcules which serve as its food.

Fig. 1s8. — Apsilits rorax.

204

L O WER INVER TEBRA TES.

There are also many other rotifers, which normally remain attached permanently
to some water plant or submerged stone. Among the attached forms we may call
attention especially to the Floscularians. They are commonly found attached to the
stems and leaves of aquatic plants. The foot-stalk, bearing the bell-shaped body, is
very long. Dr. Carpenter describes thus one of the most beautiful species, iStephan-
ocera eicJiornii. The body has five long tentacles, beset with tufts of short bristly

cilia, reminding one of the
ciliated tentacles of the
Bryozoa. The body and
foot-stalk are enclosed in
a cylindrical cell resem-
bling that of the Hydro-
zoa and Bryozoa. A com-
parison of this with other
forms, however, shows
that these tentacles are
only extensions of the
ciliated lobes which are
common to all the mem-
Ijers of these families.
The so-called cell is not
formed by a thickening
and separation of the
outer integument, but by
a glutinous secretion
from it, so that, as the
rest of the organization
is essentially conformable
to the rotiferous type, no
such passage is really es-
tablished by this animal
towards otiier grou|)S as
it is commonly supposed
to form. In the allied
genus Mellcerta the body
is protected by an artifi-
cial cell, constructed of
little pellets. Mr. Gosse,
who fortunately had an
opportunity of watching
the animal build its cell,
describes how the work is done. The ciliary wheels sweep particles into the upper
end of the digestive canal, where they are fastened together, probably by a glutinous
secretion, and moulded into a rounded pellet, which is then disgorged, and the animal,
bending over, deposits the pellet upon the edge of the wall it is building, thus imitating
the art of the bricklayer.

The Rotifera include many odd forms, among them the extraordinary spherical
creature discovered by Professor Semper in the Philijipines, and the grouji of the

Fig. 189. — F/oscuUiria oniata.

WORMS.

205

queer Asplanchnid^, rem ark able for having one opening of the digestive eanul ; but
the majority of the wheel animalcules, which the collector obtains, belong among the
relatives of the Botifer vulgaris, yet present to our inquisition a great variety of
shapes and diversity of habits. They have been divided into three families: First,
the Philodinidre, of whicli the genus Rotifer is the type ; second, Brachiouidas
{Bruchionis, Noteus, 3Iasti<jocercu, iStephanoj)s, etc.) ; third, Hydatinid^ (IL/datiiia,
Afofiocerca, JVbtommata, Dif/lena, etc.). We shall give an account of a typical species
of the second and third family each,
having already described the type of
the first.

In the Bkachionid^ the body is
broad, almost shield-like sometimes,
the foot is short and jointed, and the
integument is, in part, so hardened as
to create a so-called cara2)ax. JVoteun
quadricornis is perliaps tlie best ex-
ample of the family. The broad rump
is covered by the shell, which has
many nodules upon its surface, and is
prolonged into four horns, — two by
the head and two near the tail. Tlie
wheel forms a notched euj), and serves
to svvreep food down to the mouth at
the bottom of the cup, as well as to
act as an organ of expeditious loco-
motion.

Hijdatina senta is a classical ani-
mal, because it was principally on this
species that the illustrious Ehrenberg
studied the anatomy of this group of
animalcules. The broad body has only
a very short foot-stalk, which is forked
behind. The mouth is ai'med with
two jaws and many teeth. There are
no eye-sjjecks whatsoever. The cuticle
is delicate and soft. Ilydatina illus-
trates the extreme rapidity with which
the development of the young is ae-
com])lished. The egg is extruded
within a few hours after the rudiment
of it becomes distinctly visible. Within twelve hours more the shell bursts and tlie
young animal comes forth. In Rotifer and several other genera the young are extnuled
alive, incubation being completed witliin the parental body. In Brachiomis still a third
method prevails, the eggs remaining after their extrusion attached to the posterior end
of the body, until the young are set free. Ehrenberg has made the astounding estimate
that Hijdatina may multiply so rapidly that one hundred millions may be produced
within ten days from a single individual ! I confess that this appears to me a totally
erroneous calculation, resting upon an utter misaiiplication of the multiplication table.

Fig. 190. — No/t'us quadricornis.

206

LOWER INVERTEBRATES.

The rotifers, like a few otliers of the lower animals, have an almost incredible
power of withstanding desiccation. Api^arently, in the most unfavorable conditions of

deficient moisture, evaporation from their
bodies does not jjroceed further than to
interrupt their activity without destroying
their vitality. Apj)areiitly they may exist
in this dried condition for an indefinite
period, and resume their course of life upon
being again supplied with water. " This
fact, taken in connection with the extraor-
dinary rate of increase mentioned in the
preceding chapter, removes all difficulty in
accounting for the extent of the diffusion
of these animals, and for their occurrence
in incalculable numbers in situations where,
a few days previously, none were known
to exist ; for their entire bodies may be
wafted in a dried state by the atmosphere
from place to place," and they return to
active life whenever they encomiter neces-
Hydatina scnia ; A, female; B, male. sary conditions of moisture and warmth.

Class III. — GASTROTKICHA.

These minute worms, barely more than microscoiiic in size, are
found in quiet waters in company with other animalcules. They owe
their name to the presence of locomotive cilia upon
the under sui-face of their bodies. The number of
s])ecies is limited, and there have lieen thus far only
seven genera established, of which Icthijdium and
Clicetonotus are the most connnon. The body is
flask-shaped, and terminates in a fork formed Ijy two
short processes. The mouth lies at the front ex-
tremity, and leads into the very noticeable muscular
oesophagus. There is usually a pair of jiigmented
eye-specks in front. All the sjjecies are probably
hermaphroditic. Beyond these few anatomical de-
tails we have little knowledge about the group —
nevertheless it is ])articularly interesting because the
t}pe of organization is extremely simple, indeed, I
think the simjilcst of all the animals with an organ-
ization essentially bilaterally s^'mmctrical. We hope
that some jiatient investigator will soon work out the
development and entire life history of these worms.
Closely related to the Gastrotricha, and yet offering striking pecu-
liarities of its own, is a small marine worm, Echhioderes, which was
first discovered at Saint Malo, in 1841, by Dujardin. The bod}^ is
from a third to a half of a millimetre long. The shape of the animal.

- Ir/ttltl/tlltatl.

"n

Fjg.

lOX.—Ecluno-
deres.

WOIlMS. 207

as well as the bristles and red eye-specks on the head, and also the caudal fork, reminds
one strongly of the Gastrotricha. A false a])|iearance of segmentation or jointing of
the body is produced by ten rings of sijines. The head is quite distinctly marked off,
and can be -withdrawn into the body. The sexes are said to be distinct.

Class IV. — NEMATODA.

The well-known " vinegar eels " are typical Nematods. The true name of vinegar eel
is Leptodera oxophila, but most authors still call them Auguilhda aceti. The older
writers describe them as very abundant in vinegar,
but nowadays they are not so common. Formerly
vinegar was prepared so that a good deal of sugar
was left in solution, but at present the processes of
manufacture used eliminate nearly all the sugar,
and, morever, the vinegar is too often adulterated
with sulphuric acid, so the Leptodera has a poor
chance. The vinegar eels, however, do not live on
the vinegar, but on the fungi which grow in it, Fiu. i94.-z,t'j</'«/rm<u«y,/,;/«, viuegar
and which depend on the sugar for nutriment. If

any one wishes to observe these microscopic worms, it is only necessary to add a little
sugar and mucilage to some vinegar and allow the mixture to stand in an ojien dish
for a few days. A fungous growth a]ipears, in M'hieh the eels develoji, and they may
be seen readily by scooping up some of the fungous mass, spreading it upon a glass
slide, and examining it under the microscoije. The same worm, apparently, appears
in fermenting starch jiaste, although the paste worm has received a different sj)ecific
name, L. glutinis. The worm never exceeds a couple of millimetres in length; in
English measure it is always less than the twelfth of an inch. It is long, cylindi-ical,
transparent, and has a digestive canal which occupies nearly the whole length of its
body. At the anterior end is the long, muscular (esophagus ; in the middle lie the
elongated reproductive organs, alongside the intestines. In the female the eggs are
quite conspicuous, shining through the body wall. The external surface of the body
has a tough crust, yet a very elastic one, else the animal could not wi'iggle and twist
as it does. Now all these features are common to the nematods in general, and they
owe their very name to their thread-like shape. Indeed, despite the great number of
si:)ecies, they present a remarkable uniformity, not only in appearance, l)ut also in organ-
ization. The most noticeable variations are in the outline of the body, the armature
of the mouth, and the form of the caudal extremity. Now in all three of these
respects the Leptodera is as simple as possible ; the mouth is a simple opening, the
body a simple cylinder, and the tail simply tapers off. It is organized like one of
Mother Goose's repetitive melodies.

Nearly all the species of Leptodera and the allied Pelodera live in moist earth and
putrefying substances. Our knowledge of their curious habits is mainly due to the
experiments of Anton Schneider, whose account we rejiroduce in abstract. To obtain
the species it is only necessary to have a pot with some earth in it, it matters little of
what soil ; put a small piece of meat or pour a little blood or milk into the earth, and
keep it moist, not wet. The earth contains great numbers of the larvae, which attracted,
perhaps, by the smell, crawl to the centre of putrefaction, whei-e they soon swarm.
They become sexually mature, and the young they produce develop on the spot to

208

LOWER INVERTEBRATES.

mature worms. But after a time they are seized with a migratory instinct, and crawl off
in all directions, the young worms witli the rest. In the drier earth the young slough
their skin, but do not leave it ; on the contrary, it forms a protective ease, which the
larva inhabits until it again encounters moisture and putrefaction, when it bursts from
its imprisonment and renews the cycle of life. According to Schneider also, some
other species of these genera occasionally exchange their free life for i)arasitisra upon
the large black held snail of Eurojje and upon the common earth-worm, but in favora-
ble external surroundings leave their host again. It is but a stej) to change from this
habit to the true pai-asitic life led by most Nematoda.

The lUiabditis ui(/rove?iosa is a parasitic mendjer of the family of Angaillulidae,
and has a most remarkable life history. There are two generations of sexually mature
animals. The members of one generation are very tiny, perhaps two hundredths of
an inch long, lead a free life in moist earth or mud, and resemble anatomically the
JLeptodera. The members of the second generation grow to half an inch long, inhabit
the lungs of frogs, and were formerly supi>osed to belong to the AscaridiB, a very dis-
tinct family. Evidently something is wrong, — either our system of classification or
else nature itself. Let ns trust to the future for the resolution of our dilemma. The
first generation is developed from the eggs of the first, and vice versa. The eggs from

Fig. 195. — Anijuiliula ??"i7/Vi, wheat worm.

the parasitic form are discharged through the intestines of the host, and develop
directly into the free form ; the female of the latter, however, retains the eggs, and
the young develo]) within the parent. " She exceeds the ])elican, for the mother nour-
ishes her offsiH-ing not only with her blood, but all her internal organs break up until
nothing remains but the skin, to form a lifeless case ai-ouml the brood of squirming
young worms.-' This stage of life lasts some time, and then the young jump out and
remain perhaps for weeks in the moist earth, until they have an ojijiortunity, by way
of a frog's mouth, of getting into his lung and there growing u]i into the Ascari
nigrovenosce.

Other members of the Angnillulidie are very injurious to plants. The most noto-
rious of these enemies to husbandry is the Anguillula trilici (known also under the
name of Tylenchus tritici)., for it inhal)its and destroys the ears of wheat, ]>i-oducing
the dreaded disease known as smut. These worms were discovered about the middle
of the eighteenth century by the English mieroscopist Needham, but our present
knowledge of them is due mainly to Monsieur Davaine. In the diseased ears the grains
are malformed, small, and black ; they have a hard crust, which encloses a coi-e of
white powdery substance, which upon being moistened falls into little bodies,
which the microscope shows to be Anguillulae, but still immature. In nature the
kernel of wheat falls to the ground, gets moist and rotten, the wall breaks open,

WORMS. 209

and the worm is set free, to crawl about in the eai'th until the new grain shoots
forth. The worm then climbs up, resting motionless whenever it gets dried, but
resuming its climb as soon as moisture restores its activity, and finally reaches
the tojj while the ear is young, and there entering the parts of the flower, the worms
cause a gall-like growth to the i)lant. There they dwell, and, liaving meanwhile
become mature, the eggs are developed, deposited, and hatched out. The parents
dying off, the embryos become tlie only inhabitants of the gall and form the dust-like
substance which we mentioned at the begiiuiing of the paragraph. Tlie power of this
species, and of its immediate congeners, to withstand desiccation and to recover their
full activity upon the return of moisture, is almost incredible. This wonderful capacity
is most developed in the larvae, the adults being endowed with less resistance. It is
known that one of the galls containing larvae may be kcjit dry for over twenty years
and at the end of that jjeriod be revived by moisture. Spallanzani's experiments
showed that the loss of moisture must be gradual, for the larvae need apjiarently to
make some preparation for their long confinement. It is not to be supposed that the
worm dries up, but rather that it is able to prevent its own loss of moisture for an
indefinite period. The excessive development of this strange ability to stop the vital
processes is evidently a means by which the animal is enabled to escape what were
elsewise the fatal dangers of its life cj'cle.

The primitive type of the Nematoda is probably more nearly preserved in the
family of Enoplid^; they are not parasitic, but lead a free life; for the most part
they are marine animals. Very little is known of their habits or metamorphoses.
They are found among plants, oftentimes in snarled bunches. Some species live in
fresh water, but rarely, except in pure running streams, and others again in moist earth.
The most common genera are Enoplus and iJorijlainms. M.any of the species have
a peculiar spinning gland at the posterior end of the body and opening on the under
side of the tail. "So soon," writes Professor Schneider, "as the animal has fixed its
tail upon some support, it moves along and draws out the secretion of its gland to a
vitreous thread several lines long. One end of the thread is glued fast, on the other
floats the animal in the water." Most of the Enoplidae avoid the neighborhood of
putrefaction, but delight in pure soils and waters, in which they often abound.

The remaining families of the thread-worms are jiarasitic ; arranging them as nearly
as possilile according to the extent they depart from the type of the free forms of the
class, we have, beginning with those the least changed, Filariadse, Trichotrachelidse,
Strongylidae, Ascaridae, Mermithidre, and Gordiida. Each of the first four of these
families includes parasites very dangerous to man and the domestic animals.

Of the FiLAEiAD^ the Filaria sangiiinis-hommis is said to ha the cause of the
elephantiasis, so familiar to physicians in the oriental tropics. The larva are found in
the blood vessels and lymjshatics of man, and by clogging the jiassages imi)ede the
circulation and produce, it is asserted, the enormous enlargement or hypertrophy of
parts known as elephantiasis. It is su]iposed that the mosquitos suck into their own
bodies the larvae in the human blood ; that when the mosquitos go to the water to lay
their eggs, they soon die, and the worms escape into the water, these become mature
and produce their young, which enter the human system when the water is drunk.
Filaria (Dracunculus) medinensis, the so-called Guinea-worm, occurs in the tropical
districts of the old world, and is found parasitic in the subcutaneous tissue of man. It
is very thin, but may attain a length of several feet; only the fem.ale is known. The
parasite lies coiled up in the soft tissue, in which it produces an ulceration, and

VOL. I. — 14

210

LOWER INVERTEBRATES.

Fig. 196. — rrU-hi
si>iraHs encysted
muscle.

the discharge of tlie ulcer serves to set free the brood of young, but the history of
the species has not yet been further ehtcidated.

The Teichoteachelid Ji inchide the most dangerous by far of human parasites, tlie
one wliich most often and most rapidly proves fatal to the life of its host, the much-
feared trichina. The worm occurs in little distinct cajisules in the muscles of the
body of many animals ; now when some of the infested muscles of one animal
is eaten by another, the capsule is dissolved by the action of the digestive juices, and
the larval worms are liberated in the intestines of their new host, where in the course
of a week they become mature and then produce millions of eggs, which soon hatch
out minute larvae. The larvae shortly penetrate the walls of the intestine and wander
about through all parts of the body, injuring and irritating all the
tissues they traverse. Finally they settle down in the muscles,
penetrate the muscular fibres, feed on the substance thereof, and
grow in a few weeks to several times their original size. While
wandering and growing they produce the most serious consequences
in the health of the host, and being often present litei'ally in millions,
the accumulated effects of all the slight injuries ]iroduced by each
trichina cause the greatest suffering to their victim, and often lead
to his death within a few weeks. Still the host may be restored to
good health if he can survive the fii'st few weeks of danger; for
after the trichina! are established in the muscle fibres and have
finished their growth, there they remain for years and years, en-
closed in tough capsules, in which they lie coiled in a sjiiral. In
this state they j)roduce no serious injury, and, as after the first attacks are over, and
the inflammation they cause has subsided, the muscles and other injm-ed tissues of the
host are regenerated, there maybe a complete recovery, after passing through the first
period of danger.

Pigs, from their omnivorous habits, are peculiarly exposed to the attacks of tri-
chinae. In some German towns it was found that one pig in every three hundred or
even less was infested ; now such a pig slaughtered and made into sausages and
uncooked ham has often served to feed nearly a whole German village, and thus to
cause a veritable epidemic of trichinosis. In 1884, shortly after the exclusion of
American pork from Germany, ostensibly because of the danger of trichinae, there
occurred one of the most frightful epidemics just in the manner told above. From
one pig the ijarasites wei-e conveyed to three hun<lred and sixty-07ie known jiersons, of
whom no'less than fifty-seven died within four weeks. Tliis was in the villages around
Emersleben, Saxony, having only about sixteen humlred inhabitants. Such outbreaks
have been by no means uncommon in Germany, owing to the habit universal there of
eating raw or imperfectly cooked moat. To every jiruilent
person it has become an inviolable rule, never to eat any
sausage, pork, or ham, which has not been very thoroughly
cooked, so that any eucapsuled tricliina^ in the meat may
have been killed by the hent.

The trichina; are found in the muscles in immense num-
bers, and often closely crowded together, each worm looks
like a coiled hair, whence the name Trichina spiralis.
The oval capsules are not over a fortieth of an inch in length, while the worm
of course is very much smaller, and always coiled. They were first found by Hil-

FiG. 197. — Trichina spiralis.

WORMS.

211

ton and first named by Richard Owen, who published a very inaccurate description
of them in 1835, but the origin and dangerousness of these parasites was never sus-
pected until 1860, when the investigations of Zenker, Leuckart, I'agcnsteelici-, and
Virchow suddenly revealed the dan-
ger by ascertainuig the history of the
trichina and its pathological action.
The whole civilized world was horri-
fied at the discovery of the great and
unthought-of risk which our daily
meals involve. Everywhere the in-
foi-mation was spread, and never, per-
haps, has any subject occasioned such
universal discussion as this new know-
ledge. In the intestine the trichina
grows rapidly, the female becomes
a'bout an eiglith of an inch long, but
the male does not measure over a six-
teenth. The eggs in the female have
no shell, and develop to tiny embryos
within the body of the parent. The
adult worm is thin and tajiering to-
wards the head. A number of related
species and genera are known, but
none ai'e so dangerous as the Tri-
china spiralis, although one form, the
Trichocephalus dispar is not rare in
the human colon.

Of the Strongylid^ several
species attack man, for cxam|i!e
Kastrongylus gigas, Dochvrius dao-
denalis, etc., but the species we select
for a special biograjihy is the one so
detested by poultry raisers as the
cause of the "gapes." The ]>arasite in
question goes by the name of 'Si//i-
gamns truchealis, and inhabits the res-
piratory passages, tracheas and bronchi
of birds, living in bunches, which soon
enlarge so much that breathing be-
comes difficult to the imlucky bird,
which gasps for air, — the name
"gapes" refers to the characteristic
symptom of the disease. The geneiic
name Synganius I'efers to the j)ecu-
liarity of the small males of attaching themselves to the large females to form indis-
soluble pairs. The constant effort to dislodge the parasites by coughing serves to
expel the eggs laid by the female; the eggs are thus scattered about, and are swal-
lowed again by other birds, and thus the disease is spread. In a hennery the malady

Fto. 19%. — Syn(jam,us trachealis ; a, male; b, female.

212

LOWER INVERTEBRATES.

readily becomes an epidemic ; the uuft'eiing hens should be isolated from the rest and
kept carefully cleaned ; it is said the parasites may be dislodged by brushing out the
trachea with a feathei'.

The AsuAEiD^ also include several species long known as human parasites ; two
of these, the pin-worm, Oxyuris vermicularis, and the large round-worm, Ascaris lum-
bricoides, belong to the earliest and most familiarly known of parasites. The pin-worm
is extremely common, and very generally distributed over the world. The eggs are
so light that they are easily scattered about, and when swallowed along with some
other object, they develop in the intestines to the adult worm. The habits of
civilized life diminish the danger from these parasites, especially as modern systems
of sewage constantly remove the eggs, which jiass out with the natural evacuations.
The A. Imnbricokks grows to a large size, six or seven inches ; is cylindrical, but
tapers towards tiie head and somewhat towards the tail ; the color is reddish brown.
The animal is a parasite of the small intestine. The eggs pass out, and in water or
moist earth await the conijiletion of embryonic growth, but how the larva reaches the
place of its final development has not yet been ascertained.

The Mermithid^ and Goediid^ were long placed near to, but apart from, the
Nematoda proper, but the best opinion now groups them with this class in spite of
certain peculiarities of their anatomy and development. Both Merinis and Gordius
are commonly known as liair-worms, and are found while sexually immature in the
body cavities of various insects ; but they become mature only in the free state, Mer-
mis living in the earth, Gordius in the water. The habits of Mermis have given rise
to the belief in Europe in a rain of worms ; for often in summer after a warm rain at
night they swarm to the surface, and appear to have been indeed rained down. Thc!
larvse are parasitic in caterjiillars, but exactly how they gain entrance to the body of

their insect host is not known. The metanior]ih<ises
of Gordius are still under discussion, for 31. Villot,
who has published a long memoir on the subject,
does not agree with earlier observers. " The eggs
of Gordius variabilis" \\rites Dr. Leidy, " are ex-
truded in a delicate cord resemblino- a thread of
sewing cotton ; the eggs are very minute, and as
the parent may be a foot long, it is able to produce an enormous number of young,
Leidy estimates over six million. The development of the young is readily observed
from day to day, and it takes about a month before the process is completed. ... In
about four weeks the Gordius escapes from the egg, totally different in
appearance from the parent. The newly developed Gordius is about
jj^ of an inch long. The body is constricted just posterior to the
middle, so as to appear divided into two portions. The anterior
thicker portion of the body is cylindrical, distinctly annulated, and
contains a complex apparatus, which the animal is capable of pro-
truding and withdrawing." Meissner observed the larvaj of another
species penetrate the larvte of May flies and caddis flies. Villot main-
tains that there always follow several successive miirrations before the fig. 2^
worm reaches its last host, but his observations are not convincing.
The adult Gordius is sometimes found in the water, and country sujierstition affirms
that a horse hair has fallen in and been chancred to a worm. Wo know better!

'00. — L.irvii
Gordius,

WORMS.

213

Class V. — ACANTHOCEPHALI.

We again enter the dominion of parasitism. The Acanthocophali, or barbed-
headed worms, comprise the single genus Echinorhynchus, a genus rich in parasites
whicli infest the liigher animals. Of them all the best known is ^.^

the JScIdnorhynchus (jigas, wliich is especially inimical to the pig,
but does not hesitate to make its home in the intestines of many
other sjaecies of mammals, and oven, it is said, in man. It grows
to over a foot in length, and is, towards the middle of its body at
least, thicker than a lead pencil. Other species abound in lislies,
big and little. All Echinorhynchl (there are over one hundred spe-
cies known) have an elongated sack-like body, without any diges-
tive canal. Their essential external characteristic is the short,
more or less nearly cylindrical proboscis, which is armed with
several rows of hooks or barbs, which, like those of the tajie-
worms, serve to anchor the parasite in the tissues of its host. The
eggs are generally spindle-shaped, and are retained in the body of
the mother until the embryo is developed ; the embryo is enclosed
in several membranes, and has a bilateral armature of tiiorns around
the anterior extremity. The embryos are sujijiosed to pass the
larval state in some aquatic host ; but the life history of these ani-
mals is still very imperfectly elucidated, therefore it does not
appear desirable to attempt a fuller account of the migrations and
metamorphoses of these parasites, because such an endeavor would
lead only to an unsatisfactory compilation of fragments.

The internal anatomy of the Acanthocephali has been quite
thoroughly studied, but we have thereby only gained a knowledge
of the extraordinary singularities of their org.-niization, without ob-
taining any real clew as to their affinities with other worms. TJie
most we can safely assert is that they present some resemljlanees
with the nematods, after which we have accordingly placed tliem
in the system here adopted.

\

\^

Al

Fig. 201. — Echhinr It yn-
chus authuHs.

Class VI. — CH^TOGN^ATHI.

Along the Atlantic seaboard the skimming net may gather from the ocean's sur-
face considerable numbers of little elongated animals, perhaps half an inch or more in
length, and somewhat javelin-like in shape. They move with quick jerks, which are
highly characteristic. Examined more carefully they are seen to be almost pearly
white in color, and quite translucent. Their form is nearly rod-like, with lateral fins;
the anterior end is enlai-ged to make the head, which is further characterized by two
dark specks, the pigmented eyes, and two groups of curving hooks, acting as jaws. On
each side of the body is a horizontal membrane or projecting fin ; this lateral fin varies
considerably in size and outline in the different species, but is always most developed
on the ]iosterior half of the body, but is often subdivided, and in that case forms an
anterior and posterior fin. A similar fin projects around the tail, and is probably
merely a specialized part of the horizontal fin, which we may assume to have extended

214

LO WER IN VER TEBRA TES.

in its uiulift'cTi'iitiatt'd form along both f>i(le.s of tliii body and around the tail as a con-
tinuous flap. The posterior portion of the body is <livided off from the anterior by a
transverse se]itiim; the anterior compartment is much the longer, and contains the
simple, straight intestine, whicli terminates just behind the septum and
>.he ovaries; the smaller caudal compartment contains the male geni-
talia.

Tliese worms are jirobably related to the nematodes or thread-worms,
but their anatomical singularities are so numerous that it is well to keep
them apart. They were first desci-ibed about the middle of the last cen-
tury by a Dutch author, Martin Slabber; for nearly one hundred years
little was added to our know ledge of these worms, but, during the last
forty years, their structure an<l development have been quite thoroughly
worked up, principally by German zoologists. lUit even the com[ilete
information which we now possess has uot yet enabled us to form any
satisfactory or definite opinion as to the afKnities of the group.

The number of species known is only thirteen, whicli have been
separated into two genera, S<((jitt<t and SjjadeUa. (Some of the species,
at least, are cosmopolitau. The spawn may be obtained by confining
the pregnant animals at the proper season, in most cases the spring or
early summer. The spawn dro]>s to the bottom of the vessel and lies
there unattached. The ova are envelo]ied in a gelatinous mass, which
does not surround eacli ovum separately, but belongs to the whole mass
of eggs in common. In the sjiecies studied by Gegenbaur the process
of segmentation occupies some seven to nine days, and it is probable
that maturity is reached within a year. A singular interest attaches to
the literature u|ion the <levei()])ment of Sagitta, in that it includes a jnib-
lication by Charles Darwin, which contains one of the few serious blun-
ders committed by tlie great English naturalist. He observed certain
Vwi;|3>^ fish-eggs which he mistook for, and described in 1844 as, the eggs of this
Fig. 202. — .svr,/«- ^voriTi, and it was not until many years later that the error was corrected.

tn bipunctata. ' _ .

There is no metamorphosis, but the embryo gradu;illy assumes the a<lult
form. The animals are predaceous, feed-
ing upon small Crustacea and other pelagic
anim.als.

We ouglit to mention here, rather than
elsewhere, two other aberrant tyjies, which
liave as yet l)een only very incompletely
studied. The little information we possess
indicates that they are related to 8a<jitta,
and also to the Nematodes. The first ty])e
is known under llu' name of tlie Ch.S)tosom-
iD^, and is jtrobably the connecting link
between the Cluetognathi and thread-woi-ms
projier. There are two genera, Jihabdo-
gaster wwd O/uKtoKOi/ut, both marine, and
foimd crawling about over the surface of alg;e. The former genus lias been described
by Metschinkoff. The mature female measures only O.oG millimeters. The anterior

Fig. 203. — lihabdoiianti'v cifvotftfn ; a, iintualiire
male; b, mature female.

WORMS.

216

end of tlie body, particularly the region of the oesophagus, is very much thickened ; in
Cfuetosoma this thickening ends abruptly posteriorly. The body shows fine transverse
lines, and has hairs or bristles upon the back. The mouth is
surrounded by three lips. The male has two hooks around
the genital ajierture, which are very similar to the so-called
spicute of nematod worms. The most singular and charac-
teristic feature of CIuHosoma, however, is a double row of
short rods on the ventral side, Justin front of the anal open-
ing ; each rod has a knob at the free end. Nothing is known
of the life history of these interesting forms. Hitherto they
have been observed in Europe only, but it seems probable
that they will yet be discovered in America.

The second type, the Desmoscolecid^, is also imper-
fectly known. It jiresents some indications of segmentation
of tlie body, but whether it is really jointed like a true anne-
lid is very doubtful. We cannot do more than give a brief
descri]ition of a typical species, Desmoscolex rnitn/tiis. The
animal has a head-like enlargement of the anterior end of
the bod}-, and, beliind that, a series of protuberant rings, jiro-
ducing an appearance of segmentation. The liead carries
two pairs, and each ring (save the eleventh and fifteenth) a
single pair of bristles, which Greef states are used as locomo-
tive organs. The sexes are distinct, and may be recognized
l)y secondary external sexual characters. Three or four eogs
are laid at a time, and borne about by the female for some
while. The animal is marine.

u

(

Class VII. — NEMERTEA.

The nemerteau worms are free-living animals, usually very
much elongated in shape, but especially characterized by an
enormously long slendei- ])roboscis, which when at rest, is
withdrawn into the bod}-, but is thrown out upon slight
provocation. When one of these animals is captured, the
proboscis is often broken off and might readily be mistaken
for a second worm, for it is a long filament, which maintains
its autonomic contortions for a considerable period. The
Xemertea were long classed with the Turbellaria, but the
union with the latter was based upon gross misconceptions,
and we now know that they must stand as an independent
class, having more affinity with the true annelids than with
the iilathehninths.

We may take the well known genus Ti'tragtenima as
tyjjical of the class, although most of the forms are very
mucli larger. The species represented in our illustration
is only two millimetres long, while some nemerteans ex-
ceed a foot in length. In TatvanHtnuM the o]iening of
the mouth, and also that of the canal, in which the re- Fio 204.

\-^-t\

-Tetrastemmn olsnira

216

LOWER INVERTEBRATES.

traded proboscis lies, are situated in front on the under side ; at the front also, but
upon the upper side, are placed four groups of eye-specks, but in most forms there are
only two such groups. The proboscis occupies the centre of the body, and is the
most conspicuous of the internal organs ; in it may be distinguished the stylet, which
in the exserted proboscis projects from the tip. The presence or absence of this stylet
serves to distinguish the two sub-classes into which this group of worms is divided ; for
tlie Enopala, to which the Tetrasiemma belongs, are furnished with a stylet, while the
Anopla are without. The second sub-class includes the majority of the better known
and larger nemertean worms.

Fig. 205. — Polia crucigera.

Muddy bottoms, both in deep water and between the tides, yield to the digger
many species of this class. Perhaps the most remarkable of these thus obtainable is
the giant Cerebrutulus ingens, which is met with under stones where there is sand. It
is an enormous, smooth, flattened worm, yellowish, whitish, or flesh-colored, and some-
times grows to be ten or twelve feet long and over an inch in width. C. rosea also
occurs in similar places ; in form it resembles its larger relative, but is less flattened,
smaller, and decidedly red in color; it is often covered by adherent grains of sand.
Another species belonging to the nemerteans is also found on the New England coast
in great abundance under stones from mid-tide to high-water mark ; it is the Xemertes
socialis, a gregarious species, many of them coiling together into large clusters ; it is

WORiMS.

1

217

filiform, measuring five or six inclies in lengtli ; its color is dark ash brown or blackish,
a little lighter underneath, and it has three or four eyes in a longitudinal group on
each side of the Iiead. (Verrill.)

A very beautiful and common European species is the Polia crucigera, so called
because its dark green body is marked by crosses, made by white stripes and trans-
verse rings. Its favorite haunts are calcareous rocks
bored out and excavated by other creatures, or else it
seeks refuge among the brandies of coral, as in our
figure, which represents a very perfect specimen
drawn life size.

There is, perhaps, nothing more interesting in the
history of the nemerteaus than the curious metamor-
phoses which some of the forms accomplish, although
in other cases the development is direct. In the
former instance the larva passes through the remark-
able pilidium stage, so called, because the larva Avas
originally described as a new animal under the name
of Pilidium ; in that condition the embryo is found
swimming about in the ocean ; it is almost micro-
scopic in size, transparent and somewhat like an in-
verted bowl in sha]ie, with two flaps lianging down from the edges, one on each side;
on top a thick mobile hair, the flagellum ; the edges of the bowl and the two flaps are
fringed with delicate cilia to serve, together with the flagellum, as locomotive organs.

Fig. 206.-

Pilidium containing (n) a young
neniertean.

Class YIII. — GEPHYEEA.

The Gepliyrea are an illy-defined group of forms intermediate in many ways
between the lower worms, iiarticularly the nemertean type, and the higher worms
or annelids proper. Until very recently the Echiuridse, which Hatschek's brilliant
researches have proved to be degraded annelids, were also included in this group, —
and indeed this important rectification has not yet found its way into zoological text-
books. The only true gephyreans are those known hitherto
as the Inermes, while the Gephyrei Chajtiferi (Echiuridffi)
belong to the chaatopods (see Annelida).

The Gepliyrea are not hermaphroditic ; they are all
marine, usually have a retractile proboscis, and always have
a ring of nervous matter round the oesophagus and a ven-
tral nerve cord ; but their bodies are not segmented. The
ventral nerve cord distinctly marks an approach to a higher
type ; in the lower forms the nervous system is far less con-
centrated. The true gejihyreans com]irise two families,
Sipunculidae, having tentacles around the mouth at the end
of the proboscis, and Priapulidse without tentacles. Of the
SiPUNOULiD.E we may consider Phascolosoina typical ; an
imdetermincd European species of this genus is rejiresented
in the accompanying figure. Phascolosoma coementarium
is very common upon the sandy or shelly bottoms in deeji water along all the northern
coasts of New England. This worm takes possession of a dead shell of some small

Fig. im. — I'hiiscolosnma.

218

LOWER IN VER TEBRA TES.

gastropod, like the hermit crabs, but as the a])erture is always too hirge for its body,

it builds out the rim of the aperture until oidy a small round opening is left, through
which the worm can stretch forth the anterior extremity of its
body, or withdraw into the shell it has appropriated for its dwell-
ing. It lives permanently in its borrowed liome, dragging it about
by the ])owerful contractions of its body. The material with which
the J-'Auscolono/iia patches out the shell so as to constrict the
mouth thereof, is a hard and durable composition of sand and
mud, cenicnled togctlier b)' a secretion of the animal. When
fully extended the forward jiart of the body, or so-called proboscis,
is long and slender, and furnished close to the end with a circle of
small slender tentacles, which surround the mouth. There is a
band of minute spinules just behind the mouth. When the worm
grows too large for its habitation, instead of
exchanging it for a larger shell, as do the
hermit crabs, it gradually extends its tube
outward from the mouth of the shell, a labor
sometimes rudely interrupted by a fish swal-
lowing the worm, shell and all.
Priapidits., of which we give an admirable figure, is tlie tyjje

of the second family, the Peiapulij)^. Even its exteriuil form

indicates tlie necessity of placing it ajiart from Sijiunculids.

The anterior club-sha])ed portion of the body is the ]iroboscis

with numerous dentate ridges. The tail is covered with nu-
merous round papillai. The genus is common in deep water

along the shores of northern Eurojie, and burrows a hole in sandy

bottoms, where it resides as ha])pily as the Phuscolosomu in its

stolen shell, and leads an equally uninteresting life.

The genus Plwroiiis stands quite apart, and in fact has been
classed with the annelids by some writers, but our jtresent know-
ledge indicates rather affinities with the gephyreans. It lives
in tubes on the sea bottom, and has a crown of tentacles around
the mouth. Its larva, known as Actinotroclia, is a remarkable
creature, with long ciliated arms about its body, and changing into the adult worm by
turning itself apparently inside out.

Flu. i;o». - I'hnscolos
via coemeutariam.

Fio. -(Mt. — Prlapnlus.

Class IX. — ANNELIDA.

We pass now to the last of the worms in the ascending series, the large and varied
class of segmented or jointed worms, which includes the leeches, the common earth
worms, and an immense number of marine, fresh water and terrestrial species, which
attract the naturalist by the wonders of their organization, development and habits.
Every sort of life which is open to crawling and swinmiing creatures is led l»y one
or another of the annelids; some grovel in the earth or live in nnid ; some take refuge
amid rocks and corals; some wander freely over the ocean, and are gaily decorated ;
others are mean parasites, feeding and dwelling on larger creatui-es, and leading
greedy, selfish lazy lives, like human criminals, stealing the property of otheis.

WORMS. 219

T)ie annelids attain the higlu'st anatoniieal grade known within the verniian ty])0.
By this I mean that tlieir organs are more complicated, or as one says, specialized.
This advance is recognizable in all parts ; the sensory apparatns is mnch perfected,
especially the eye and ear have become capable of better functions than in lower
worms. The nervous system has distinct centres, or ganglia, of which the largest
lies in the head and is comparable with a true brain, ami exhibits, npon ])ro]ier micro-
scopical examination, considerable complexity of structure. The jieculiai-ity, however,
which is most striking, and which gives the name to the class, is tiie division of the
body into a succession of more or less sinular shoit }iarts, known as rings, joints, or,
more correctly, as segments. In the common earlh-worm these joints are readily seen,
being marked on the outside. Tlie essential part of a true segment is a distinct
division of the muscles, but besides we also find a separate nerve-centre for each seg-
ment, a separate excretory organ, sej)arate markings and separate external appendages,
all repeated for each segment. In the grou]i known as the Polycha'ta, the external
appendages are numerous and conspicuous, and serve to accentuate, in the eyes of
even a hasty observer, the serial re]ietition of parts, which is the most obvious result
of the segmentation of the body.

The annelids fall naturally into three well marked sub-classes, the Archiannelida,
having no bristles and no suckers ; the Chajtopoda, having bristles upon their sides,
and the leeches, having two suckers, one around the mouth and the other on the ven-
tral side of the posterior extremity.

Sub-Class I. — Archiannelida.

This sub-class iucludes a small number of worms, whose affinities and ini])ortance
as the nearest living representatives of the archetype of the
segmented worms was first pointed out by Hatschek, to
whom science is also indebted for the recognition of the
grou]i, which is only just beginning to find its way into
text books (1884). The best-known form is Polygovditis.
a long, slender worm, without bristles or a])])endages nor
external joints, although its body is segmented. Its larva
was long tV.uiiliar to naturalists as a free swimming pelagic
embrvo, very minute indeed, and always desiu'iiated as Fig. Lno.-Po/.</wr(K«s larva; a,

^ J ' J r^ anus; m, nioutli; s, stoniacii.

Loven's larva. Many an attempt was made to trace out

the mctamor])hoses of this larva, but always unsuccessfully until within a few years,

when it was discovered to be the young of PolygorcUus.

Sub-Class II. — Ch^topoda.

These worms may be easily recognized by their jointed bodies, and by the presence
of two rows of spines on each side thereof. The places of insertion for the
spines are often protuberant, and sometimes project so far as to form false limbs —
(parapodia). We then have on each segment four of these outgrowths, each bearing
a single spine or a group of spines. When upon each protuberance there is but a
single, or very few spines, the worm belongs to the Oligochasta, the lower order of
the sub-class ; in the Oligochasta the protuberances are but slightly if at all marked;
in the other and higher order, the Polychaeta, there are usually true parapodia.

220

LOWER INVERTEBRATES.

movable like a limb and each having at the end a cluster of many bristles, often of
bizarre shapes and brilliant shades of color.

Order I. — OLIGOCH^TA.

The Oligochfeta are all hermaplirodites, are vi'ithout cephalic appendages, and have
no armature around the mouth. The best known of the order, and indeed of the
whole class of Annelida, is the familiar earth-worm, the favorite victim of an art
which serves to hire boys to brooks, and to beti-ay fishes into the frying-pan. We

owe to Darwin a series of
most interesting observa-
tions on the habits of earth-
worms, and the role they
play in the economy of
nature, and we are almost
equally indebted to the
acute studies of Von Hen-
sen. The characteristics
of earth-worms are, the ab-
sence of ajipendages, the
large number of small seg-
ments, the small size and
number of the bristles, tlie
w^ant of sense organs, and
the development of a belt
or clitellus ; this is a thick-
ened portion of the body,
not far bvhiiid the head,
and having a smooth, glis-
tening surface.

Ziumbricus terrestris is
common both in Europe
and America. I quote
Linnteus' description as
given in Turton's quaint
translation : " Inhabits decayed wood and the common soil, which by perfoi-ating it
renders fit to receive the rain ; devours the cotyledons of plants and wanders about by
night ; is the food of moles, hedgehogs, and various birds. Body with about one
hundred and forty rings, each of which contains four pair of prickles, not visible to the
eye but discoverable by the touch ; when expanded is convex each side, and when
contracted is fiattish beneath, with a red canal dow'n the whole body ; the belt is
wrinkled and jiorous ; mouth placed beneath the proboscis." Now this description
is altogether inadequate for the discrimination of the species, nevertheless we will let
it pass ; still less satisfactory are the remarks on the habits, wliich we must amend and
extend. First of all let us add that "belt" means the clitellus, which in this species
includes six segments, so fused that the external demrireations are obliterated.

Earth-worms are essentially burrowing animals, nocturnal in their habits, althotigh
they sometimes leave their holes and crawl over the ground to a new locality, and also

Fig. 211. — Piirapodia of Ht^ttronartis ; c, upper, f/, lower divisions.

WORMS. 221

are occasionnlly active during the daytime. They are exceedingly dejicndcnt on
moisture, for a single day in tlie dry air Ivills them, wliile on the other liand tliey will
survive in water for a long jieriod; hence, whenever there comes a "dry spell," they
all retreat into the lower stratum of soil not yet parched by the heat upon the sur-
face. I have known them to retire to a depth of four feet in a period of prolonged
drought, which completely exhausted the moisture to that dei)tli. In wintei-, too, they
always go down below the frost and make a little hollow or chamber at the bottom of
their burrow, in which they coil up to hibernate, often several of them getting to-
gether. They usually carry down with them a few small stones, for what purpose is
not known. In summer they live close to the surface, if it is not too dry, shutting up
the mouths of their tubes with little pellets gathered from about, or with their own
castings. Keeping quiet during the day, they emerge at night, stretching forth the
antei-ior end of their bodies and exploring the neighborhood ; keeping, liowevei', most
of their long selves within doors and ]-etreating entirely upon the least alarm ; a jar of
the soil, or light falling upon them, is sufficient to awaken their timidity and cause an
instantaneous retraction of the protruded part of their bodies. But their habit of
remaining so near the surface renders their timidity, even, an insufficient protection,
for they are often discovered and dragged forth by robins and otlier birds, which,
unlike L^ither,. esteem the diet of worms. The Jyicmbrici are omnivoroiis; beefsteak,
cabbage, fruit, green leaves and dead, dirt, stones, broken glass are all swallowed with
an impartiality that would do credit to Aristides. But, although it has its preferences
as to what it will eat, Liimbricus is not content without dirt and small stones, or other
hard, indigestible objects, together with more nutritious fare. A]iparently from the
dirt it is able to extract some m'atter, perhaps to assimilate the microscopic organisms
it contains ; tlie stones probably act as gi'inders, serving to crush the food proper and
mix it thoroughly with the digestive juices. The earth-worm, then, ]iasses through its
intestine pretty much everything in and on the ground, which can possilily get
through ; but it discharges its castings upon the surface, a manure which is universally
known as vegetable mould, but would be more correctly termed if called animal
mould. Now, as the worms burrow in every direction, they constantly bring up from
below and deposit on the surface, so that the superficial layer grows slowly but
steadily. Thus it happens that if ashes are strewn on a field the earth-worm castings
are dejiosited over them, gradually burying them until they finally disajipear. In his
book on the earth-worm, Mr. Darwin gives many instances of this apparent subsidence
which, under the most fa\-oral)le circumstances, goes on at the rate of two or three
tenths of an inch per annum. Wo quote the following account from his pages :
" Ne.ar Maer Hill in Staffordshire, quick-lime had been spread about the year 1827,
thickly, over a field of good ]iasturo land, which h.ad not since been jdoughed. Some
square holes were dug in this field in the beginning of October 1837, and the sections
showed a layer of turf, formed by the matted roots of the grasses, one half inch in
thickness, beneath which, at a depth of two and a half inches (or three inches from
the surface), a layer of lime in powder or in small lumjis could be distinctly seen run-
ning all round the vertical sides of the holes." Even large objects, big stones and ex-
tensive pavements, are gradually buried by the worms, because their burrows extend
underneath, and by their collajise let the overlying oVijeet sink, while their castings
raise the surface around it. " When we behold," writes Mr. Darwin, "a wide, turf-
covered expanse, we sliotdd remember that its smoothness, on which so much of its
beauty depends, is mainly due to all the inequalities having been slowly levelled by

922

LOWER INVERTEBRATES.

^^&='s

Fig. 212. — Tower of castings of Perlchceta
near Nice.

worms. It is a m.arvellous reflection tliat the whole of the suiierficial mould over any
ri(;li expanse has passed, and will ai;ain pass, every few years, through the bodies of
worms. The jjlougii is one of the most ancient and most valuable of man's inven-
tions, but long before lie existed the land was
in fact regularly ]iloiigiied, and still continues
to be thus j)louglied, by earth-worms. It may
be doubted whether there are many other ani-
mals wliich have ])layed so important a part in
the history of the world as have these lowly
organized creatures."

The amount of the castings is strikingly
shown by tliose earth-worms wliich belong to
the genus Perichata, for these animals deposit
their ejections in remarkable towers, which
rise like turrets, with their summits often
broader than their bases, to a lieight of two
and a half and even tliree inches. Near Nice,
in France, these towers abound in extraordin-
ary numbers, and are probably formed by a
species naturalized from the east. Mr. Scott
complains of the trouble they cause in the
botanic garden at Bombay: "Some of the
finest of our lawns can be kept in anything
like order only by being almost daily rolled;
if left undisturbed for a few days they become studded with large
castings." The i)eriod during which worms near Calcutta display
such extraordinary activity lasts for only a little over two months,
namely, during the cool season after the rains. Ilensen believes
that the importance of the earth-worm is not so much in the pre-
paration of humus as in making passages for the roots of plants,
and he describes the manner in wliich the burrows arc utilized by
plants. Indeed we owe to him the demonstration of the relation
of the worms to the fertility of the soil, increasing it as just men-
tioned.

During the mating season the earth-worm leaves liis burrow,
seeking a mate. The eggs are laid in the ground, and are two or
three lines in length. Our figure delineates one of them with the
enclosed mature embryo, and its top closed hy a valve-like struc-
ture adapted to facilitate the escape of the worm. The shell
generally contains several yolks, but only one of them usually de-
velops. It was once erroneously believed th.at Lumhricus might
bo multiplied by mechanical section, but although the front part
of a divided worm survives, the back jiart dies, unless, indeed,
when the front includes only the head and a few segments, for
then the survival is reversed, the posterior division living on and
manufacturing a new head for itself.

The aquatic Oligochasta (Limicola?) are very numerous both in species and indi-
viduals, and have been separated into four f.imilics. 1. Piireokyctid^, of which the

Fig. 213. — Eggs of
earthworm.

WORMS.

type is a very long and slender worm, discovered by Professor Leydig, which dis{)luys
a marked predilection for deep wells. As far as I am aware it lias hitherto been
found only in GeiToany. '2. Tubificid^. The common and graceful Tubi/'ex makes
an interesting inhabitant of a small fresh-water aquarium. It is easily obtained by
digging up some dark mud from the bottom of almost any meadow brook, and then
placing it with water in a jar; when the settling is eonqileted the worms will soon
reconstruct their long tubes which run down from the surface of the mud; they will
then stretch forth tiieir long slender bodies, which undulate incessantly until some dis-
turbance causes the frightened worm to jerk back into its domicile. The animal is long
and slender as a thread, somewhat reddish in color and transparent. With a lens
the segments of its body may be readily distinguished, and the little lateral bristles;
those of the lower row are forked and hooked : similar bristles, together with simple
hair-shaped ones, form the upjier row. Along the New England coast tlie allied genus
Vlitellio is common, being, unlike Tubif(i.i\ an inhabitant of the ocean ; it is found, in

njrten mcnkcanuii.

company with two or three otlier cognate genera, under stones and decaying sea-weeds
near high-water mark.

The members of the third family, KNcHvrK.Ein.t:, live in the earth, rotten woods,
waters of swamps and the ocean. The red-blooded J'achi/driltts maj' be taken as
typical ; it being a common marine genus. Tiie last family, the Naid^e, comprises
the best-known and nn)st interesting members of the order, the two chief genera, Naiit
and Chietoyaster, li.aving been studied again and again by naturalists during the last cen-
tury and a half, their wonderful reproduction by transverse di\ision always possessing
a vivid interest. The Naidie are small, transparent worms, which may be readil}'^ cap-
tured by scooping blindly through the plants growing in fresli water, among which
these creatures swim abt)ut. Many of them have a long snout or liorn growing out
from the head. Very common is the JSfais proboscidea., which has a relatively immense
appendage " proaking out before its eyes." This long trunk is used to feel the way.
Another member of the same geinis, however, has a simple rounded head. The genus
itself is easilv reco<;ruzed by the fact that the tipjier row of bristles on each side are
hair-like, while the lower row are hooked ; f'hri^toyaster is characterized by having no
dorsal, but only the ventr.'d row of bristles. Both forms lay large eggs singly, en-
closing them ill ]irotective capsules. It is, however, the asexual reproduction of these
worms which is so interesthm;. Tiiere ajipears in the midst of the body a little zone
of tissue, occupying at first less sjiace than one of the segments between v\ liieli it is
interpolated. The microsco])e shows that this tissue is of ;t very elementary character,
consisting of so-called embryonic or germinal cells. Gradually the tissue of this inter-
polated zone transforms itself into muscles, nerves, etc., and, growing meanwhile, it
forms in front a new tail jiiece to ])atch out the anterior half of the worm, and be-
hind it forms a new head for the posterior half of the original body. The zone then

224

LOWER INVERTEBRATES.

breaks, and there are now two worms, one with a new tail, the other with a new head.
In JVals it is very common to see several "budding zones" at once in various stages
of develojjmeut. But the process of division does not always jsroceed in precisely
the same way. The genus Z,unihriculus, one of the Tuliitieid;v, also multijjlies by
transverse division, but it breaks in two first, and then develops the germinating tissue
out of which the missing parts are redeveloped for each individual, a new tail for the
front, and a new head for the hinder of the two. The new hind end arises as a little
bud, consisting of new cells and ciliated over its surface, and subsequently forms the
requisite number of segments. If the head is cut off it is reformed — a most conve-

li'iluciliL; !•> Ii:->lijli, flilaiiift.!.

uient arrangement, which, were it feasible with man, would essentially diminish the
inconveniences of capital punishment.

The delicate fresh-water annelids are much preyed upon by carnivorous insect
larvfe, and it is not uncommon to see a T>!/tiscus larva, far instance, seize one in its
jaws and snip the poor worm in two, one half escaping. This mishap, which would
be fatal to most animals, is onlj' a temporary inconvenience to a N^als or Lumhricidus.
It is evident that their extraordinary re]irodnctlve endownrents must be one of the
most important factors in the preservation of the species. Bonnet, one of the most
accurate of observers, found that the process of regeneration is completed within a
week, and proved that one Avorm, divided into several pieces, might produce, nnder
favorable circumstances, an equal number of new com]>lete individuals, so that some-
times the very act of destruction, as in the fabled hydra, multiplies instead of annihi-
latinirthe victim.

WORMS.

226

Order II. — POLYCH^TA.

The members of this order are generally dioecious, and pass through striking
metamorphoses in the course of tlieir development. The head is conspicuous on
account of the feelers, cirri, and
gills, which are often very promi-
nent. They are nearly all ma-
rine. They far exceed all other
woi'nis in the variety of sjiecies
and the diversity of their lives :
indeed within our limits it is
utterly impossible to refer even
to all the families of the Poly-
chseta, unless we should content
ourselves with a bare catalogue.
Roughly speaking, a polyeha'tous
annelid may be recognized liy its
jointed bod}-, the false feet with
numerous bristles, and the j)os-
session of cephalic tentacles. T]}e order has two main divisions: 1, Sedentaria or
TubicoliE ; 2, Errantia, — the former with fifteen, the latter with twelve families.

Fl«. 216. — Head ami anterior segments of JJiojiatra ciqirea.

Sub-Order I. — Tubicol^e.

This sub-order owes its name to the general habit of building a tube in which the
worm lives. The dwelling is con-
structed, now of one kind, now of ,
anothei-, of foreign particles, accord-
ing to the tastes and haljits t)f the
builder, who cements his matei-ials
tirgcther by a seci'etion of his own
body, or sometimes the secretion
itself hardens, making a tube with-
out extraneous adjuncts. From the
fact that their lives are spent in
this ai'mor, the antei-ior end of the
body becomes highly specialized,
and is usually very different from
the moi'e posterior segments.

The handsome TerebeUa (Ani-
]Mtrite) ornata of oui' North At-
lantic coast, a large and interesting

Fig. 217. — tvstoiWps worm, is common both amoiic: and

(jmiitVii, a tube- "-

worm removed under rocks, and on muddy shores.

from its tube.

It constructs firm tubes out of the

Fig. 218. — Awphitrite oniata.

consolidated mud and sand in which it resides, casting cylinders of mud out of the
orifice. It grows to be twelve or fifteen inches in length, and is usually flesh-colored,

VOL. I. — 15

226

LOWER INVERTEBRATES.

Fig. 219. — Ettchmie elegans.

although variable in hue from reddish to orange and dark brown. From the head
spring very numerous flesh-colored tentacles, and three pairs of large feathered gills,
which are bright red from the blood showing through them. The tentacles are capa-
y. ble of great extension, and may be stretched out to a length
^ of eight or ten inches. Tiiey are incessantly in motion, ap-
parently to gather food and materials for tube-building. This
sjjecies may be considered a type of the large family of Terre-
liELLii)^, and possesses the following features characteristic
of the family : The body is thicker in front, the thin jiosterior
extremity bears no bristles ; the tentacles are filiform ; the
head is not marked off from the body; the gills are confined
to a few anterior segments ; the bristles are short, those of
the upper row hair-like, of the lower, hooked.

Euchone elegans is a beautiful species found on the New
England coast. When expanded, the }iale yellow or green-
ish branchia3 are recurved and connected by a broad thin
membrane. The body anteriorly is I'eddisli, changing into
flesh color and then into a darker green or brown as we pro-
ceed posteriorly. The species lives in water from five to
thirty fathoms in depth, and makes slender tubes covered
with fine sand.

In the large family of the Serpulid.e also, the gills are
confined to the anterior end of the body, and are covered
with cilia, which maintain a stream of water, which sweeps
food down towards the mouth, which is placed at the base of the gills. The head
is usually set off from the body by a collar; all the bristles are hair-like,
except those on the anterior half of tlie lower row. Their larvsd life is
free-swimming, but when they settle down they excrete a calcareous
shell which the worms enlarge subsequently to meet the necessities of
the growing inhabitants. The secretion and shaping of the tube are
performed principally by the basal portion of the gills. Tiie round,
crooked tubes made by the American Serpula dianthus are often found
on the under surfaces and siiies of stones, and even in more exposed situ-
ations,— always near low-water mark. When disturbed, the worm sud-
denly withdraws its beautiful wreath of gills, and closes the aperture of
its tube with a curious plug, called the operculum, — the portcullis of
its castle. The branchiie, when fully disj)Iayed, reveal their elegance
of form and color; they are a round cluster, jiarted into symmetrical
halves, some eighteen delicate feathered filaments on each side. The
colors are extremely variable, but always brilliant ; usunllv the branchire
are purplish at the base, with narrow bands of light red or yellowish
green ; further from the centre the filaments are trans\ersely bandeil
witli pur]ilish-brown, which alternates with yellowish-green ; in another
variety they are all citron-yellow, and in yet another ,'dl whitish, banded
with brown.

Very different is the abundant Cli/iiieiicUd torqwiUi, which is jtlain in
shape though ])retty in color. It belongs to the Maldanid.e, Polj'chffita in which all the
external appendages are very much reduced. Chjmenella constructs long tubes of agglu-

w

Fig. 220. — vhj-
metirlla tor-
quata.

WORMS.

227

tiuated saud, rather avoiding muddy bottoms. It loves quiet, and often seeks a home
among the roots of eel grass.- It is usually pale red, with bauds of bright red around
the swollen parts of the segments, but it is most readily
recognized by the collar on the fifth ring and the peculiar
funnel appended to the tail. There still remain a host of
curious genera, Sternaspis, ManayunJda, Polydora, Cirrat-
tiltcs, Capitdla, and many others, which we would fain de-
scribe, were it not for the i)ainful conviction that the general
reader's interest in worms, even in those that are polycha?-
tous, is exhaustible. We content ourselves, therefore, with
a trio of brief allusions; first, to the lug-worm, Areiiicola
marina, which is eagerly sought after as bait by English
fishermen, who dig it from the lioles it excavates in the
sands. On our coast it occurs north of Cajie Cod, but is
not used in fishing. The branchise are confined to the cen-
tral portion of the body, where they form on each side a
series of small tufts, remarkable, during the life of the crea-
ture, for their brilliant red color. It is a ty}ie of the family
closely related to the Clymenella, above described. The second form is the Spi-
rorbis, one of the Serpulidte, whose white, coiled tubes might easily be Tiiistaken

Fig. 221. — StertKispis fossm:

Fig. 222. — Serimla cantorhiplicata.

for a snail shell. They occur on rocks, shells, etc., lint ai-e most numerous on bits
of rock-weed {Fucus) thrown up from shallow water. Each individual worm is
as pretty and delicate as any species of Serpula, and, like the members of that genus.

228

L 0 WEE IN VER TEBRA TES.

Fig. ^23. — Cirratulus grandis.

wlien it retracts it closes its calcareous tube with an oj)crculuin. Over half a dozen
species are found on our northern coasts. The last form is Cisteiddes, or, as it is

called in the older works,
Pectinana. Our common
species, C. gouldii, is light
red or flesh color, hand-
somely mottled with dark
red and blue. This species
forms long conical tubes of
sand, which are remarkable
in the fact that the grains
of which they are composed
are built up, a single layer
in thickness, " like minia-
ture masonry, and bound
together by a waterproof
cement." The animal is
shown in Fig. 217.

Sub-Oeder II. — Er-

RANTIA.

The Errantia are active
and fierce beasts of jirey,
of which the Nekeid.e and Nkptiiyu.e may be regarded as the central type. The para-
podia are large movable limbs, and bear numerous bristles varied in shape and color.
Tlie tentacles on the head are often of several sorts, and the segments of the body may
vary in different regions, so that an anterior portion of the body looks very different
from another posterior, as is so strikingly exemplified in Heteronereis and its allies; the
segments of the bodies may also have gills of various kinds; in some cases these gills
are long and delicate filaments which entirely change the j)hysiognomy of the worm.

The term N'ereis was given by Linnaius to a group of annelids, which he charac-
terized as having an elongated vermiform body, furnished with soft, well-develo])ed
••ippenilages, and a head bearing eyes and tentacles. He thus included nearly all the
Errantia under one genus, and the tradition of the Linnaean name still lingers in the
habit of naturalists, who use the term Nereis or Nereid as a vague designation. The
genus has now been very much reduced, by cutting off hundreds of its original mem-
bers to establish them under numerous new genera, so that the genus N'ereis of to-day
is but a very small fragment of the original one. This has been the general fate of
all Linne's names, so that while we have kept the form, we have rejected the sub-
stance, because the essence of his system of nomenclature was to give two names, one
to indicate the general place of the form in the animal kingdom, the other to desig-
nate the species; l)ut the modern genera, luilike the Linnasan, are no longer general
but special, and one of the chief merits of binomial nomenclature has been done away
with.

Nereis pelagica is common on both si<les of the North Atlantic, and is among the
longest and best known of vermes, but on the New England coast the much larger
Nereis virens is more readily found, for it lives in muddy and shelly sand between.

MARINE WORMS.

Hetermereis smardce. Amplucora sabella. Arenicota marh

WORM.'S.

229

Fig. 224. —Head and jaws of
Nereis virens.

tides, preferring, however, to be near low water. N] virens grows to a lengtli of
eighteen inches or more. The color is dull bluish-green, with an ii'idescent tinge of
red and other brilliant hues ; the large lamellae or gills along
the sides are greenish anteriorly, but further back often be-
come bright red, owing to the numerous blood-vessels which.
they contain. It is a very active and voracious worm, terrible
to smaller animals, upon which it preys, capturing them by its
large proboscis, which it suddenly thrusts out, seizing its vic-
tim with the two large jaws which arm the tip of its eflicient
weajion of attack ; the ]iroboscis is then
withdrawn, and the food torn and mas-
ticated at leisure. These large worms,
called " clam-worms " by the fishermen,
are frequently dug out of their burrows
and eagerly devoured by tautog, scup
and other fishes, — in nature it is ever
thus, the eaters are in the end themselves

eaten. In Nereis the proboscidean armature emulates in strength
and sharpness the jaws of the ant-lion or some of the more
formidable carnivorous beetles ; neai-ly all the fi'ee-swimming
Polyclueta are similarly wea]ioned, and sometimes even more
formitlably. Thus, in I'hyllodoce ma.viUosa, the fangs of a tiger
seem to have been conjoined with the cutting teeth of a shark,
to ]>erfect such a model of carnivorous dentition as can find no
rival in the animal creation. The JSfereis does not always con-
fine itself to its burrovr, but, like all its relatives, frequently goes
a-jourueying. It is a nocturnal traveller, and at certain times
swims about in vast numbers near the surface of the ocean ;
]irobably this habit has some connection with the rej)roduction.
The life history of Nereis is still very obscure, for in some cases
it produces sexually young which become Nereis ; in other cases
there intervenes what is known as the Heteronereis stage ; Hetero-
nereis again is capable of reproduction, and apjiarently the same
species may assume different forms ; moreover Nereis is found
as a hermaphrodite as well as a unisexual animal. Now since the
connection of these forms with one another has not yet been satis-
factorily determined, the whole history of the manifold possible
changes is in confusion.
Very different is it in regard to Autolijtus, whose vital career, at least for the pres-
ent, is more comprehensible. The genus may serve also as the type of the Syllid^,
one of the chief families of the order, and remarkable for the great length of the
dorsal cirri of the body-segments. The eggs of Autoh/tiis jiroduce an asexual indi-
vidual, which multiplies by division, the anterior end remaining the asexual worm,
while the posterior individual is divided off and becomes male or female as the case
may be. We have here a ]nire example of alternation of generations, a phenomenon
first recognized aljont half a. century ago. The individual born from the egg has
neither the form nor value — that is to say, the physiological significance — of a sexual
adult, but propagates itself by budding, division, or internal gemmation. Of this we

FiS. 223. — Plii/llodoce.

230

LO WER IN VER TEBRA TES.

have already given various instances in the sections referring to parasitic species
among the lower worms. In I'omojjtei-is, a pretty, transjiarent, pelagic creature, the

false feet are very long and thick, while two long cirri spring
from the first segment so that the outline of the animal is
bizarre.

Another tyjie altogether is shown by the scale-bearing
annelids, ApuRODixiDJi ; the upper parapodia, or false feet,
carry large scales, which lie over the back of the animal
and form an imbricated covering, serving the double pur-
pose of protection and respiration. The most common of
our species in New England is probably the Lepidonotus
squamatiis, which inhabits the rocky shores of bays and
sounds, wliere they
may be found hiding
in crevices or on the
under side of stones.
It has twelve pairs of
rough scales on its
back, while its cousin
L. sitblevis has the
same ii u m b e r, but
smooth, and is found,
though less abund-
antly, in the same lo-
calities as the first-
mentioned species.
In many members of
this family, however, the bristles are greatly de-
veloped, in Hermione so as to partially, in Aphro-
dite so as to completely, hide the scales under ^
felting of hair. Nothing can exceed the splendor
of the colors that ornament some of these hairs ;
" they yield, indeed, in no respect to the most gor-
geous tints of troj)ical birds, or to the brilliant
decorations of insects : green, yellow, and orange,
blue, purple, and scarlet — all the hues of Iris
play ujjon them with the changing light." In Ajihroditv the res)iirat<>ry function of
the scales is evident ; they exhibit periodical movements of elevation and depression ;
as they are overspread by a coating of felting, readily jiermeable to the water, the
space between the scales is filled with filtered water while they are elevated ; when
they are again depressed the water is forcibly emitted at the posterior end of the
body, and the back, which serves as an organ of respiration, is thus washed by fresh
water. Although these animals are not active, yet they are highly organized, and
are to be considered the ti])-top of the world of worms, no slight dignity. Tliey
are rather inactive com]iared with many of their relatives, and are usually very dirty,
so that repeated ^vashings are necessary to uncover their natural beauties. Among
worms, also, high rank does not ensure personal cleanliness.

Pig. 226. — AutoUjtus cormttus,
male.

Fig. 227. — Hi-rmione hystrix.

WORMS.

231

SS,

The EcHiURiD^, wliicli were formerly classed with the Gephyreans, are now known
to be true annelids, but their precise affinities are uncertain, so we will slip tlicm in by
appendix. They are easily recognized by the
pair of hooked liristles on the ventral surface,
and by the two crowns of bristles which occur
around the caudal extremity of some forms.
The three principal genera are Echkiris, Tlutl-
assema and JJonel/ia. The last-mentioned is
very striking in a])])earance, as will be seen by
the figure of lio/ief/iu viridis. Oskar Schniiilt,
referring to his visit to the Dalmatian island
Sesina, writes: "I noticed aljout a foot under
water, beneath a lai-ge stone, an intensely green
worm-like moving creature; I quickly lifted
the stone, and my supposed worm revealed
itself as the two-pi-onged jjrobosL'is of Houellia.
We kept it alive in a basin for a day, and never
tired of watching its movements." The body
is covered with little warts, and, like the pro-
boscis, is vivid green ; it is capable of manifold
contractions and constrictions, and the proboscis
is an even greater proteus, and may stretch out
in large specimens to half a yard in length.

Myzostoma is another puzzle to zoologists,
but is best guessed to be a degenerated para-
sitic annelid. The genus includes a consider-
able number of species which are all external
parasites of the Comatulas ; they are small,
disc-shaped, have four pairs of lateral suckers
on the ventral surface, and a retractile papil-
lated prolioseis, and there are five pairs of
cirrus-ljearing false feet. Fig. 2L'h. — ii«iit»;<f r/iii/is.

Sub-Class III. — Enteropneusti.

There now remains only one aberrant type for us to consider, namely, the whale's
tongue. The singular and little known ainmals we have studied as isolated forms do
not fall readily into any of the great classes, and this very fact of their standing so
much apart renders them so much the more interesting to the thoughtful naturalist.
Many of these species are rare, and it becomes therefore the more desirable to call
general attention to them, in order that they may be sought and found by those who
might otherwise let pi'ecicnis opportunities go by unutilized. Very few of them have
yet been recorded from America, but there cannot be much question tliat many of
them, together with others equally singular but yet unknown forms, will, in the future,
be discovered in our fauna.

The whale's tongue, Bakmofjlossiis, so named from a fancied resemblance, is a
very interesting animal to the scientific zoologist. The adult worm was originally
discovered at Naples ; the free-swimming embryo was subsequently named Tornaria,

232

L 0 WER IN VER TEBRA TES.

and was long eoiisiclered to be the larva of a stai-fisli, until Motschnikoff established
its real affinities by tracing out its metamorphosis into the adult. The shape of the

transparent larva is well shown in the
magnified drawing; it is just large
enough to be recognized by the naked
eye by those familiar with it. It may
be caught in July and August by skim-
ming the ocean surface with a fine net.
]\luch as it differs from the adult worm,
it yet passes by a series of gradual
changes into the mature animal, which
inhabits muddy bottoms between the
tides. HalMiuylussus is, I am con-
vinced, a modified annelid, although
its precise relationshijis are obscure,
especially on account of the singular-
ities of the nervous system. It has v.
long, tapering, fragile body, the an-
terior half somewhat flattened, the posterior rounded ; at the
anterior extremity is a large, jjedunculated, top-shaped proboscis,
followed by a thickened ring or collar; behind the collar follow
the gills, a complicated set of branchial ojienings, recalling some-
what the branchiae of the tunicates. Now gills mark an advance
in organization from the ^■el•mian towards the vertebrate type,
and Halanof/lossus interests us scientifically just for this reason, that it appears in
some respects a connecting link between widely separated divisions of the animal
kiuLrdoni.

Fig, 230. — lUilanoijlossns
viinutus.

Sub-Class IV. — Discophoei.

The sucker-bearing annelids, or Hirudinei, or leeches, are segmented worms adapted
to a parasitic or semi-j>arasitic existence. They are all blood-suckers, veritable vam-
pires, and to most persons the mere thought of their habit is revolting; but the anti-
pathy they excite is not an altogether well-founded emotion, for they have their role
to perform, and man has converted them into his servants, and
given them a medical office, the duties of which they discharge
with praiseworthy alacrity. The leeches have been the theme
of one of the most singular of zoological delusions, in that they
have been considered to be related to the Tremadota. I know
no reason whatsoever for this queer conjunction, which is worthy
of the time when a whale was called a fish. It is true that both
leeches and flukes have suckers, but there all anatomical resem-
blance ceases. The leeches are true segmented worms, but the
transverse lines visil>le on tlie external surface of the body do
not mark off the segments, but, on the contrary, hide the true
Fig. 2J1. — Mukei ami jaws ioints ; hcnce their internal anatomv must be stu<lied before the

ot leech. • p , . . . * , "IT

true jij.'in of their organization can be recognized. In general
shape we find that they are somewliat flattened ; that they are usually broadest poste-
riorly, tapering oft' rapidly towards the tail, slowly towards the head ; there is a sucker

WORMS. 283

around the mouth, which is armed with jaws, and a larger one at the tail ; they are
generally dark folored, very much mottled, often having fine lines and dots of bright
hues ; they are jiroperly aquatic, and occur in both fresh and salt water.

There are three families, of the first of which, the GNATHOBDELUDJi, the medical
leech, Hiritdo tnedicinalis, is typical. The variety known as officinalis, measures,
when at rest, some three or four inches. The color of the species is greenish or '
olive green, with six rust-red, thread-like longitudinal bands, speckled with black;
ventral surface, greenish yellow, spotted with black. The mouth has three radiating
jaws, with saw-like edges ; when the animals bite through the skin, the wound
made consists of three cuts radiating from a common centre, each jaw making
a separate slit. The head is furnished with ten eyes and other special sense organs.
The natural habitat of the common leech is in swamps and brooks where the water
flows slowly; stagnant pools are misuited to it; it prcj-s on all vertebrates, both
fishes and amphibia, and on mammals which come to the water to drink or bathe.
It fastens itself upon its victim by means of its suckers, tlien cuts the skin, fastens
its oral sucker over the wound, and j)umps away until it lias comjiletely gorged
itself with l)lood, distending enormously its elastic body, when it loosens its hold
and drops off. Its attacks cause very little pain ; boys in bathing are often feasted
ujion without being aware of it until they see the dark foe against the light skin.
It is this power of extracting blood almost pauilessly which has induced ]iliysi-
cians to put them in requisition. They are generally kept by apothecaries, and sup-
plying the market has become a considerable industry in western France. In that
country it is said that they have leech plantations, swamjiy territories, wliich are care-
fully freed from all animals that might destroy the leeches, such as large frogs and
certain fishes. To nourish them, worn out horses and cattle are purchased and driven
into the leech enclosures, in which they are left to perish, death coming soon from loss
of blood, and preceded by jn-obably very little pain. The custom is not so humane as
one would be glad to demand, but, on the other hand, there is no reason to sujipose
that it inflicts great suffering on the horses, etc. The leeches are collected in the fall,
and, to a less extent, in the spring; for if gathered in summer they do not bear trans-
portation well. In autumn, however, they ai-e in the best condition, and, if captured
then, will survive months without food if jiroperly cared for. The aniiinil casts its
skin verv frequentlv, and i'e(]uires something to rub and scr;qie against, to remove the
old slough, hence the}' must be sujiplied with plants and soil through which to crawl,
as well as water. They move about either by crawling with the aid of their suckers
somewhat in the fashion of an inch-worm, or else by swimming, at which they are
adepts, but they eviilently prefer to have a firm hold. Sometimes they jilant them-
selves by the jiosterior sucker, and, stretching out their body, throw it into undulations,
Aviiicli ]iass from the head liackward, and are sustained, an uuintei-rnpted succession of
waves, for long periods. When reposing, they assume all sorts of attitudes, to look at
some of which inakes one's back ache. The common way to catch them is for a man
to stand in the water with bare feet and legs, then stir up tlie mud around him and
pluck off those leeches which fasten upon him ; some of these collectors become quite
bloodless and sickly. Other modes of capture have been tried, but the belief that
leeches must be captured upon the human skin still prevails, and leech culture there-
fore still goes on according to the ancient .and semi-barbaric rules.

Tlie egn-s are laid in the ground; in tlie spring the leeches burrow into the moist
earth, a little above the water level. Towards the end of June tjiey form their co-

■2ii4 LOWER INVEllTEBllATES.

coons or egg-capsules, in eacli of wliich arc several yolks, so that, when the young
hatcli out at the end of five or six weeks, several are born at once, and inunediately
make their way to the water. They grow very slowly. It is said that five years
elapse before they attain their full size ; they may live for twenty years.

Our waters contain many leeches similar to Hirudo ; most of them belong to tlie
genera Nephelis and Hmmopis. A giant among them is the big, spotted MacrostO)num
of our ponds. In southern Asia there live also terrestrial forms.

"Of all tlie plagues," writes Sir J. Emerson Tennent in liis charming book on
Ceylon, "which beset the traveller in tlie rising grounds of Ceylon, the most detested
are tho land leeches {HcLmadipsa cei/lonica). They are not frequent in the plains,
which are too hot and dry for them, but amongst the rank vegetation in the lower
ranges of the hill country, which is kept damp by frequent showers, they are found in
tormenting ]irofusion. They are terrestrial, never visiting ponds or streams. In size
they are about an inch in length and as tine as a common knitting needle; but
they are capable of distension till they equal a quill in thickness, and attain a length
of nearly two inches. Tlieir structure is so flexible that they can insinuate themselves
through tlie meshes of tlie finest stocking, not only seizing on the feet and anldes, but
ascending to the back and throat, and fastening on the tenderest parts of the bodj'.
In order to exclude them, the coffee planters, who live among these pests, are obliged
to envelop their legs in 'leech-gaiters' made of closely woven cloth. The natives
smear their bodies with oil, tobacco, ashes, or lemon juice, the latter serving not only
to stop the How of blood, but also to expedite the healing of the wounds. In moving,
the land leeches have the power of planting one extremity on the earth and raising the
other jierpendicularly to watch for their victim. Such is their vigilance and instinct,
that, on the approach of a passer-by to a spot which they infest, they may be seen
amongst the grass and fallen leaves on the edge of a native path, poised erect, and
prepared for their attack on man and horse. . . . Their size is so insignificant, and
the wound they make is so skilfully punctured, that both are generally imjiercejitible,
and tlie first intimation of their onslaught is the trickling of the blood, or a chill feel-
ing of the leech when it begins to hang heavily on the skin from being distended with
its repast. Horses are driven wild by them, and stamji the ground in fury to shake
them from tlieir fetlocks, to which they hang in bloody tassels. The bare legs of the
palankin bearers and coolies are a favorite resort; and as their hands are too much
engaged to be spared to pull tliera off, the leeches hang like bunches of grapes round
their ankles. . . . Both Marshall and Davy mention that during the march of
troops in the mountains, when the Kandyans were in rebellion, in 1818, the soldiers,
and especially the jMadras Sepoys, with the pioneers and coolies, suffered so severely
from this cause that numbers perished."

"One circumstance regarding these laud-leeches is remarkable and unex]ilained ;
they are helpless without moisture, and in the hills, where they abound at all other
times, they entirely disappear during long droughts; yet reajipear instantaneously
at the very first fall of rain, and in spots previously parched, where not one was visi-
ble an hour before, a single shower is sufficient to reproduce them in thousands.
Whence do they re-appear? May they, like the rotifers, be dried up and preserved
for an indefinite period, resuming their vital activity on the mere recurrence of mois-
ture?"

The second family is distinguished by having a proboscis, and has, therefore, been
named Riiynchobdelud/E, of which the very common fresh-water Clepsine is a good

WORMS.

23'5

illustration. Clepsine is remarkable because it carries its young about for some time
attached to its belly. Pontohddla is a marine representative of the family, noticeable
on account of the large size of the anterior sucker and the warts over its body. This
greenish-gray leech lives on I'ays, and is ap])arently a lazy creature with dull senses.
Its powerful muscles enable it to fasten itself upon a rock and sustain its body
in a horizontal position for a long time, but it prefers to hang down, with the head
rolled up.

Leeches are related to fisheries in three ways. Some of the large, blood-sucking
forms, such as Macrobdella and Ilirudo, attack many fishes directly, even when of con-
siderable size, and destroy them very quickly hj sucking their blood ; some genera,
like Icthyobddla and C ijstohranclms, are true parasites, and often, when numerous, do
the fish great injurj^ Others, among which belong Clepsine and NepJielis, destroy
small molluscs and worms, which might otherwise become the food of fishes. On the
other hand, the leeches are in their turn fed upon by the white fish of the lakes, and
probably other fishes (Verril).

Here we must close, although we would gladly narrate the biographies of 3Ialacob-
della, Uranchiobdella, Histriobdella and Acanthobdella — but we must leave the four
'Bdella's in the stables; we have driven far and rapidly through a large province of
nature's realm, pausing to catch glini]ises of a few of her " sights ; " let us hope
not to be of those travellers who "do" a country only to forget its appearance and
character.

Chaeles S. Minot.

^0/^fmk

Polycirni.s eximms, a tube worm with extended tentacles.

236 LOWER INVERTEBRATES.

Branch VI. — MOLLUSCOIDEA.

Among the forms of disputed position occur two well-marked groups of aquatic
animals, the Brachiopoda and the Polyzoa. In the older works the former of these
was included among the Mollusca, while the second was accorded a place along with
the hydroids in the heterogeneous group of Zoophytes. The next step was to recog-
nize the affinities of the two, and, as a consequence, the Polyzoa wei'e placed alongside
the Biaehii)]Joda, as members of the great group INIollusca. Then embryology was
invoked, and, led by certain resemblances, many naturalists separated the brachiopods
from the molluscs and gave them a place among the worms, the Polyzoa being dragged
along with them. At present the tendency seems to be to recognize the affinity of
the two groups to both the worms and the molluscs, while assigning them a place
intermediate between the two.

At first sight the Polyzoa and the Brachiopoda seem widely different, but a deeper
knowledge reveals many and important ])oints of contact, esjieeially in their early
stages. They are all, with few exceptions, attached to some sub-aquatic object. In
tlie adult all traces of metameric segmentation are lost. The tentacular apparatus
is ciliated, and is borne uj)on a circular disc, or a two-armed process arising from the
oral region. The alimentary canal forms a single loop, the mouth .and anus (when
the latter is present) being near each other. The principal nervous centre is a
ganglion just beneath the oesophagus.

The larv£e of each, though ])resenting themselves in various forms, can be reduced
to a common type, consisting of a body divided into two regions by a ring of cilia,
in the anterior of which is the mouth, and not infrequently the anus as well. This
larva can be but little removed from the trochozoon, the hypothetical ancestor of the
worms and molluscs. Some recent investigations tend to show that the relationships
supposed to exist between the two groups are really those of analogy, and not of
homology, and that the Polyzoa have some connection with the rotifers, a group here
treated of among the worms.

Class I. — POLYZOA.

The term Polyzoa, which means many animals, is highly appropriate for the group
of aquatic forms which we now take up, for they, with a very few exceptions, form
colonies composed of many individuals united in a common stock. Another name,
which was applied but a year later, is Bryozoa, or luoss-aniinals, a term no less apt,
but debarred from use hy the law of priority which g'o\'erns scientific nomenclature.
In general appearance many of the grou|i closely resemble the hydroids, and especi-
ally the sertularians. Like them, they have a com]iound structure, .and are enveloped
by a cutictil.ar sheath, while the circle of tentacles, which in life ])rojects from the
openings of the little cu]is, still further strengthens the similarity, and affords a justi-
fication for their association with those lower forms by the older n.aturalists. But
when we come to study the anatomy and the development of these anim.als, im]iortant
differences at once show themselves, and the resemblances which at first struck us so
forcibly are seen to be of a merely superficial character.

POLYZOA.

237

As we have just said, most of tlie Polyzoa form colonies, the size of whieh is
increased by budding, exactly as with the sertularians. In form they vary greatly ;
some, as Gemellaria, forming branching tree-lilce colonies, some, like Memhvanipora.,
spreading in flat sheets over the surface of submarine objects, while others, of which
we may mention Alcyonidiuni, form soft and moss-like sheaths upon the rock-weed
between tide marks. In Rhahdophura^ Laguncula, etc., a creejiing root-stalk is
formed, from which arise the cells, in a manner whicli strikingly resembles that of

some of the campanularian hydroids;
while in Loxosoma the individuals
are separate, and no colonies occur.

The chitinous or calcareous skele-
ton is composed of a series of cups,
each of which contains one of the
y])ides, or individuals of the colony.
Eacli polypide is fastened to the interior of
its cell, but the mode of attachment is such
that it can, at will, partially extend itself or, at
the approach of danger, it can withdraw all itssoft
and delicate organs. To better afford i>rotection from
external harm, each cell of the colony is frequently
?d with strong teeth or long s]iines, or there may even
n operculum develojied, a little lid, which, when the ani-
ls retracted, closes the opening through which the body
nds itself at other times.

When the poly})ide is extended, the most jtrominent fea-
ture is a disc, known as the lophophore, from which arises a
more or less circular row of tentacles. Each of these ten-
tacles is ciliated, and the constant motion of these small
organs produces in the surrounding water currents which
flow to the mouth, which in some is situated within, in others
without, the circle of tentacles. The mouth communicates
with a large jiharynx, which in turn em])ties into the oesopha-
gus, the distinction between these two being frequently em-
])hasized by the presence of a valve. In several forms the
irsophagus terminates posteriorly in a muscular gizzaivl, the
function of which is to thoroughly triturate the food before
it enters the stomach, the next division of the alimentary
tract. The stomach is lined with small follicles, wdiich are
regarded as he]iatie in function, while its upper jtortion bears
numerous cilia, which, by their constant motion, keep the
food in a state of agitation. The stomach is flexed upon
itself, and after the food is digested, the excrementa are
passed to the intestine, and thence out at the vent, which is ])laeed close to the
mouth.

No heart or circulatory organs exists in the Polyzoa, but the products of digestion
pass through the walls of the stomach into the body cavity, where they bathe the
various portions of the body. The nervous system is chiefly composed of a central
ganglion placed between the mouth and the anus. In some forms, nervous cords have

Fig. 232. — Aratomy of Paludi-
cella i^hrevberfjii; a, tentacles;
b, oesophagus; c, anus; ij, stom-
ach; ?», muscles; o, felnale, t,
male, reproductive organs.

238

LOWER IN VER TEBRA TES.

1>'1G. 23a. —A portion ot Srrupo-
ceUaria/ero^, with (((.) vibra-
cula.

been describetl, connecting the various individuals of the colony, and although the

nervous nature of these cords has been disputed, it is evident that some means of

inter-communication exists, for there is frequently such a
unison in the movenicnts of the various members of a stock
that no other ex|ilanatiou is possible. Nothing definite is
known of the organs of sensation. The muscular system is
well developed, the most prominent portions being the re-
tractors and jirotractors of the lophophore.

Possibly the structures known as avicularia and vibracula
are the most interesting to the layman, on account of their
motions and problematical functions. These organs are not
found in all forms. The vibracula are long, whip-like appen-
dages, which are attached to the cells of the colony by a single
joint, and which, moved by appropriate muscles at the base,
keep uj) a constant lashing motion. The avicularia, as is
partially indicated by their name, are shaped like the head of

a bird, with fixed upper and movable lower mandibles. These

avicularia are either directly attached to the cell, or are ele-
vated on a short stalk, and, in life, keep in constant motion,

o])ening and closing the mandibles, thus rendering a colony of

some such form as liiigula a most interesting object under the

microscope. The purposes of these organs are as yet uncer-
tain. It has been suggested th.at the constant lashing of the

vibracula serves to clean foreign matter from the colony. The

avicularia are frequently seen to seize small aquatic objects,

but as they cannot carry the prey thus caught to the mouth,

the part which tiiey play in the nutrition of the polyjiide is

at least indirect. Mr. Gosse, the entertaining English writci-

on natural history, has suggested, with considerable jilausi-

bility, that the decay of the objects caught by the avicularia

attracts other organisms to the vicinity, thus bringing them

within the influence of the currents produced l)y the cilia on

the tentacles, ami thus to tiie mouth.

The Polyzoa reproduce both by budding and by eggs.

Usually the buds remain attached to the parent stock, thus

causing it to increase in size ; but in one or two forms the buds

become separated from the parent, and form distinct indi-
viduals. Closely allied to this budding

,, I. ^. i! i i 1 1 i Fig. 234. — Poitinii of i?«f/w.'<i,

process is the formation of StatoblastS. showing birds" heads or avif-

Fio.-z^.-statoiiast. ^hese are modified buds (and not true _ "''"'"•

eggs), wliich are produced agamogenetically, the purpose of
which, like the statoblasts of sponges previously described, is to perpetuate the
species during the winter, or through a period of dry weather. The statoblasts arise
from the funiculus, or cord which connects the stomach with the cell. As they
increase in size, they become invested with a thick, horny brown enveloiie, which in
many forms is ornamented by slender spines terminating Avitli hooks, which more or
less vividly recdl the flakes of an .•mchor. Late in the autumn the fresh-water poly-
zoan dies, and then the statoblasts are set free to perpetuate the colony in the following

POLYZOA.

239

sprino-. Then, under the influence of the warmth, the statoblast hatches with its
organs ah-eady well develo])ed. At first it swims freely through the water, but soon
it becomes attached to some submerged object, with which henceforth its fortunes are
inseparably united. It now develops its cai)sule, and soon a bud is seen upon one side,
which eventually grows into an individual, inidistinguishable from the parent. Tliis
process is again and again repeated, until a large colony is formed, either extending
its branches like a tree, or incrusting some submerged object with a gelatinous or cal-
careous envelope, forming in some instances clusters several feet in diameter and
eight or more instances in thickness. This same process
of budding takes place in the marine genera.

We do not yet know enough about the development
of the eggs of the Polyzoa to reconcile all the widely dif-
ferent features of the embryology. Still, all the various
forms of larv£e may be reduced to a body surrounded by
a ring of cilia (possibly corresponding to the lophojihore),
which divides it into two faces. On one of these is the moutli, and in some the anus
also. On the other is a ciliated disc, by which, it may lie, the animal attaches itself.

Tlie Polyzoa first a])pear in time in the silurian I'ocks, and have jiersisted to the
present day. The oldest forms known are referable to grou]is now living. At one
time it was thought that the graptolites might belong here, but now the best authori-
ties are inclined to place them among the hydroids

Fig. '2'3G. — Larva of Alcyonldhim.

Sub-Class I. — Entoprocta.

The jirimary feature characterizing this group is the jjosition of the vent, which is
placed within the circle of tentacles, thus indicating that the group is the lowest of
the sub-classes, a feature which is characteristic of the larvaj of some of the higher
groups here persisting in the adult, as can be seen by comparing the figure of Cypho-

nautes (fig. 246), which is the larva of Jfemliruin-
pom, with that illustrating the anatomy of the adult
Pedicellina (fig. 237). In this group the tentacles
are not retractile, but can be rolled uji.

In the Pedicellinid.e there is a creeping root-
stock, from wliich at intervals the long-stalked indi-
viduals arise and the colony increases by budding.
On our coasts is found PedicelUna americaiui, which
creejjs over (jther Polyzoa, hydroids, etc., forming
small white branching stems, the stalked individuals
resembling so many clubs. Urnatella is a fresh-
water genus, represented, so far as is at present
known, by only a single species, Urtiatdla gracilis,
from the Schuylkill River at Philadelphia. In this
briglitly colored form the cells are borne on the ex-
stalks. In former years the species Avas very abun-
dant just below the dam which sup])lies the city of Philadelphia with water, but now,
doubtless owing to the j)ollution of the river by sewage, sjiecimens are but rarely
found.

The LoxosOMiD^, which were first made known in 18G3, are long-stalked, solitary

Fio. 237. — Anatomy oj Pidicellijia ; h,
blood pouch; m, mouth; v, ganglion; 7%
rectum; a-, stomach; f, tentacles.

tremities of long noded branchini

240

L 0 WER IN VER TEBRA TES.

entoproctous Polyzoa, without a partition between the cell and tlic stalk, and witli a
cement gland on the end of the stalk. The genus Loxosoma is I'ejjresented in Euro-
pean waters by several species, distinguished, among other peculiarities, by the num-
ber of tentacles. Tliese forms attach themselves to sertularians and other Polyzoa,
and reproduce by budding. These buds, instead of remaining attached to the parent
as in other Polyzoa, become separated, and settle down to begin life for themselves.

Sub-Class II. — Ectopeocta.

This division, which contains by far the greater ])roportion of the Polyzoa, is far
more complicated in its structure than the Entoprocta. A most important distinction
is found in the fact that the anus is placed outside the circular or horseshoe-shaped
ring of tentacles. There is further a tentacular sheath. Other characters will be
noticed in our subsequent account of the two orders into which the sub-class is
divided.

Oeder I. — GYMNOL^MATA.

The forms embraced in this order are almost wholly marine. They agree
in liaving the ring of tentacles in a complete circle and in the absence of a
lophophore, a structure which will be mentioned when treating of the other order.
Statoblasts are but rarely present (as in the fresh-water genus Paludicella.) The
larva' leave the eggs as ciliated embryos, which swim freely for a time, and then settle
down to spend the remainder of their lives attached to some submerged object, form-
ing a colony by the process of budding. In the shape and constitution of the external
skeleton the greatest diversity exists, it being sometimes calcareous, sometimes
chitinous, and at others gelatinous. The order is divided into three sub-orders,
founded upon the shape and ornamentation of the mouth of the cell containing the
polypide.

Sub-Okder I. — Cyclostomata.

The cyclostomatous Polyzoa, as is indicated by the name, embraces those forms in

which the mouth of the cell is round and un-
armed by spines, and in which, when the ani-
mal is retracted, the opening is not closed by
an operculum. Most of the genera and species
are extinct, yet many are found living in the
colder seas, the sub-order reaching its highest
develo]iment in Arctic waters. The living
forms aie arranged in six families, three of
which (CeisiadjE, DiASTOPORiDiE, and Tuuu-
liporid.e) are re])resented
on the Xew England coast.
Crisia ehurnea, of which
we give enlarged figures,
is an ivory white, calca-
reous species, frequently
found attached to seaweeds in tide-pools and in deeper water. In the Tubulijioridae
the cells are placed in rows, arranged transversely to the branches. S])ecies of Tiihu-

FlG. 23S. — Crisia eburnea.

Fig. 239. — Iihnoiiea.

POLYZOA. 241

lipora and Idmonea are common in the shallow waters north of Cajie Cod, one species
of tlie former genus extending to the south of that barrier.

Sub-Okdek II. — Ctenostomata.

Here the cell is closed, after the retraction of the pulyjiide, by jirocesses of the
tentacular sheath, or by bristle-like projections. Two families, represented by several
species, occur on our coasts. In the Alcyonidiid^ the colony forms a fleshy or mem-
braneous mass very irregular in form. Our most common species is Alri/onkUum,
/lifpidtim, and scarcely less frequent is the closely related A. Jiirsutiim. These forms
are found most abundant surrounding the stems of the rock-weed (J^'ncus), between
tide-marks. The former is thicker, and niay be readily recognized by the slender
reddish bristles which surrounil the mouth of the cells. In the second species each
cell forms a small soft papilla, from the centre of which the [tolypide protrudes itself.
A. ramosum is a large branching species, which not infrequently forms colonies over
a foot in length, the branches sometimes being nearly half an incli in diameter. In
the Vesciculaeid^e the general form of the colony is a creeping or upright branch-
ing mass, from which the cells arise as free sheaths. In Vescicularia tliese sheatlis are
sessile upon the stock, while in Farella they are seated upon short peduncles. Several
species of the former are common upon our coasts, while Farella familiaris, which
extends from Long Island Sound to Europe, is found on rocks and sea-weed. " When
it surrounds the stems of small alga?, the whitish pedicels project outwards, in all di-
rections, and thus produce the ajipearanee of a delicate chenille cord." The members
of the family Paludicellid.e are inhabitants of fresh water.

Sub-Order III. — Chilostomata.

The Chilostomata are characterized by having the mouth of tlie horny or calcareous
cell capable of being closed by a lid, while the oral area is usually membranous, rather
than horny. It is in this group alone that we meet with the vibracula and avicularia,
which we have already described, but their presence is not universal. It is divided
into four super-families, the lowest being the CELLFLARINA. Here the horny oi'
slightly calcareous cells are tubular, funnel-shaped, the lower attached
extremity being tubular or conical. In ^ta anguinea, which may be
taken as the type of the family JETmM, the tubular cells, with the mouths
at the apex, arise fi'om a creeping root-stalk, while in Eucrate chclata,
representing the Eucratid^, the mouth of the cell is one side of the
extremity, and the cells are arranged in a single row. In Gemellaria
loricata, a large form common in shallow water noi'th of Cape Cod, we
have a close similarity to the last species, except that the cells are
arranged in pairs, back to back. In the Eucratida; no vibracula or
avicularia are present, while in the Celhjlaeid.e these structures are fig. -2i(i.-r,em-
usually f<nmd. The colony branches dichotomously, and the cells are «"'"•"'■

arranged in two or more rows. It is represented in our waters by species of Cellu-
laria and Caberea.

In the BifELLAEiD.E the cells are conical or qu.adrangular, .and the large, laterally
placed mouth is placed near the median axis. Our most prominent species of this
family belong to the genus Bugula. Here the branches are arranged in a spiral, giving

VOL. I. — 16

242

L 0 WER IN VER 1 'EBR .1 7 '£ S.

.'\

f|-

.]#

Fic. 241.— Titiijnfd tarritii.

the colony a very graceful appearance. Occasionally the species are found in the
greatest abuiulance, flumes leading to tide-mills being especially favorable localities.

These forms are most fa\orable for studying the motions
of the avicularia.

The second super-family, the FLUSTRINA, embraces
flattened forms with quad)-;ite cells and an even sm-face.
Very frequently the col-
ony is reduced to a mere
incrusting scale njion
stones or sea-vv'eeds. Our
most common forms be-
long to the genus Meui-
brcoiipora, whicli is sepa-
rated from LepraUa in
having the anterior cell-
wall membranous instead
of calcareous, as in that
Ljenus. The edges of the
cells are ornamented by
long and slender spines, the numbers and shape vary-
ing according to the species. The sjiecies of Flustra
assume a branching form, the branches being broad
and flat.

The ESCHARINA are Polyzoa with a lateral
oj)ening to the quadrate or half-oval cell. The first

f a ni i 1 }-,

J the EscHARipoEiDyE, has the cells rhomboid

or cylindrical, while the opening is semi-

cii'cular, with the anteritn- margin s])lit or

perforated with a median pore. In the

i Myriozoid^ we have erect forms, with

^H more or less cylindrical branches, the ])os-

terior margin of the mouth of each cell

being excavated. Myriozoum subc/racile,

which we figure, is found north of Cajie

_; Cod. The Eschakid.e have the principal

3M mouth of the cell semicircidar or round,

^ the secondary being reduced to accom-

= modate the occasional avicularia. The

colony may be either in the form of round

^^ branches or of broad, flat divisions, the cells

^ , occupying the opposite sides. The Dis-

COPOBID.'E have oval or rhomboid cells, with
t.^J.'^-J^ semicircular mouths, the posterior mar-
gins of which are armed with one or more
spines.

In the CELLEPORINA the colony is calcareous, the cells being rhombical or
oval, and the mouth is terminal. Two well-marked families exist. The first, Celi.e-

FlG. 2i2. ^ Membranipora pUosa; a, por-
tion of a colony; b, side view of a single
cell; c, a single polypidea; 11 enlarged.

- / y 7 ilttr

POLYZOA.

243

PORID^, has the colon}' lamellar and irregular, iiicrusting the surfaces of suh-marine
objects, or upright and branching. In Celkpora an aviciilarium exists in the median
line, just behind the posterior margin
of the mouth of the cell, while in Cel-
leporaria it is absent. The Retepor-
iD^ are graceful forms, in which the
cells unite to form a flat, leaf-like col-
ony, which is perforated with numei'- lk^^('^s^'^^('"~7^ 1(^\
ous oval openings. _j:«s. %\ xV/ / \\J

Order II.

— PHYLACTOL^E-
MATA.

This order embraces the fresh-water .
Polyzoa proper, none of its members
being found in the sea. They have
the tentacles arranged on a horseshoe-
shaped loi^hophore, while the mouth may be closed by a tongue-shaped lid, known as
the epistome, which is placed just above the rudimentary brain. In size these forms

Fig. 244. — Mfjrio::oitm subgracUe.

hUtjioia celhUosa

are much larger than their marine relatives, while their general appearance is much
more uniform. They are found beneath stones in running brooks, attached to sub-
merged logs in lakes and ponds, and in the case of Cristatella the whole colony is free,
and has the power of motion as a whole. The number of species known, from the

244

L 0 WER IN VER TEBRA TES.

Fig. 246. — Ci/pJionautes, younj
of Membra'nipora ; 7n, mouth
A', stomach.

Fig. 247. — Fredri-
cella.

whole world, is relatively small, not over fifty, of which North America possesses about
a dozen. The names which the different genera have received are more musical than

in some other groups, owing to the diminu-
tive " ella," with which most of them ter-
minate.

The CeistatellidvE are readily distin-
guished by their free condition. They form
large colonies, the individuals being arranged
in concentric circles or ovals, on the upper
surface, while the lower is modified into a
contractile fieshy foot, of use to the colony
in its slow, creejjing motion. Two species
are known in this country, and one in
Europe, both belonging to the genus Vrlstatella.

The family Plumatellid^, which is much larger, embraces sessile
forms, the various genera of which are distinguished by the gelatinous or ])archment-like
nature of the cells, the structure of the statoblasts (with or without sjiines), and the
massive or branching nature of the colony. Four genera, Fredricella, Plumatella,
Lophopus^ and Pectinatella, are represented in the waters of eastern North America.

Sub-Class III. — Podostomata.

Tlie genus lihabdopleura so differs from the other Polyzoa as to warrant the erec-
tion of a sub-class for its reception. It approaches most closely of all the class to the
MoUusca. It consists of a creeping root-stalk, of a chitinous nature, from which arise
the tubular branching cells. Each cell has a round terminal mouth, and the walls of
the cell are annulated for some distance below the mouth. The various cells of the
colony are separated by transverse partitions. The long arms of the lophojihore bear
two series of tentacles, and resemble somewhat those of the Phylactolasmata, but
much more closely those of the brachiopods. The animal is fastened to its cell by a
long, contractile filament, by which it draws its body down out of the way of harm.
When the danger is past, according to Sars it literally climbs out of its tube, by means
of a disc between the arms, which ajipears to rejiresent the ejiistome of the fresh-
water forms. Cephalodiscus is the only other genus of the sub-class. It was dredged
by the ' Challenger ' expedition.

Class II. — BRACmOPODA.

The shells of the brachiopods, at first sight, closely resemble those of the lamelli-
branch molluscs, and hence it is not strange that these forms were for so long a time
associated together. Indeed, even at the present time most geologists fail to recognize
the important differences, a fact probably due to their ignorance of the anatomy and
embryology of the living forms.

The brachiopods, which are all marine, are provided with a bivalve shell, but the
two valves of the shell are alwaj's dissimilar, while the two sides of each valve are
alike, just the reverse of what ol)tains among the lamellibranchs. In the chemical
structure of the shell, .also, an important fact is to be noted, that phosphate of lime is
present in much larger proportion than in that of any true- mollusc. Most of the

BRACHIOPODS.

245

brachiopods are fastened to some marine object by a fleshy peduncle, which passes
out between the valves in tlie centre of the hinge line, or in a corresponding position
in those forms where no true hinge is present.

The inside of the shell is lined by a membrane, which is called the mantle, from
its resemblance to a similar structure among the molluscs. Close up to the hinge
line is the visceral mass, which is small in proportion to the size of the shell.
The mouth is situated in the centre of the visceral mass. The cesophagus communi-
cates with the stomach, into which open the ducts from the liver, while the intestine,
in most forms, is short, and ends without any external opening, but in others is longer,
and terminates in a vent on the right side of the mouth. The alimentary tract is
sujiported in the spacious body cavity by a membrane analogous to the mesentery of
the vertebrates. The body cavity is lined with cilia, which keep the contained fluids
in constant motion, while prolongations of the cavity extend hito the lobes of the
mantle, thus forming a I'udimentary circulatory system. The body cavity communi-

FiG. 24S. — Anatomy of Waldhamia; d, arms; m, ?i, peiliiiiole; p, a;soiihagus; 7, stomach; r, liver; s, intestine.

cates with the exterior by two or four ducts, which in the oMer works were described
as hearts, but it is now known that they are urogenital in function, and should he
compared with the segmental organs of worms.

Tiie nervous system is much better developed than in the Polyzoa, and consists of
an (Esophageal ring and, in the lower forms, two lateral cords ; in the liigher, of a
mt)re complex structure. No sense organs are known. The muscles which open and
close the shell and control the other
movements of the animal are well
developed.

There now remains to be de-
scribed, in this hasty sketch of the
anatomy of the group, the arms,
which in almost all forms are large.
These arms, from which the grouji receives its name (brachiopoda, arm-footed), arise
on either side of the mouth, corresponding to the lophophore of the Polyzoan, and.

Fig. 249. — Development of Terebratulhta ; a, three segment stage;
b, attached; c, middle segment folding up to envelop the first;
rf, t% later stages.

246

LOWER INVERTEBRATES.

like that structure, supi)ort a greater or less number of tentacles, like a fringe. These
arms are long, and, in order to be accommodated within the shell they are folded, or
coiled in a spiral. In some species they can be slightly protruded from the shell, but
the extent of motion, in most forms, is small, since they are frequently supported upon
a calcareous process of the shell itself, a structure frequently preserved in fossil
forms. The Brachiopoda are divided into two groups, accordingly as the two valves
of the shell are hinoed or not.

Fig. 250. — Linijula jii/rtnn'ufatn.

Order I. — INARTICULATA.

In the Inarticulata, or Ecardiuia as it is sometimes called, the hinge of the shell is
wanting, as is also any calcareous support to the arms. The alimentary canal is com-
plete, the anus emptying into one side of the chamber of the mantle. The borders
of the mantle are completely separate.

The family Lixgultd.e embraces forms which have lived on the earth since almost
the earliest geological times. Tlie genus Lingula apjieared in the rocks of the Pots-
dam group, at the very base of the lower silurian, and to-day species of Lingula an;
found in various warmer seas. In these the thin, horny valves of the shell are nearly

equal and similar, while from near the
point of attachment of the valves pro-
ceeds a long, fleshy stalk, or peduncle.
The best-known s\>ecies oi Xinr/ula to-day
is X. ■pyraniidata, occurring on the sandy
shores of Virginia and Korth Carolina.
In this form the stem is about two inches
in length. The animal lives with its
peduncle buried in the sand, in water
of from one to ten fathoms, while the
shells, in the centre of which is the
mouth, project above the bottom. Not oidy is the genus a long-lived one, but the
individuals themselves are able to withstand very adverse circumstances. Speci-
mens can readily be carried to all parts of the country, and Professor Morse relates
that individuals which he obtained survived after being several hours loose in his
pocket. While our species of Lingula is small, those found in the eastern seas reach
a length of nearly a foot. The development of our species has been studied, and Dr.
Brooks says, "that the recent and fossil shells of the various species of Crania, Dix-
cina, Lingula, Lingulella, Obolus, and other hingeless brachiopods, furnish a series of
adult forms representing all the changes through which the
outline of the shell of Lingula ligramidata passed during
its development." Of Lingula there are now seventeen
living species, and a large number fossil. All the othei'
genera of the family, Obolus, IJngulella, etc., are extinct.

The DiscmiD^, in which the shell is neai-ly circular
and the peduncle passes through the flat lower valve, have
only a single existing genus, TJiscina. These forms ex-
ternally closely resemble the genus Anomia, a true mollusc.
The Craj^iid^, represented in the seas of Europe by the
genus Crania, ha\e no peduncle. Fourteen species of the two families are found ii
the existing seas.

Fig. 2o1. — Upper valve of Crania
anomala, with the animal.

BRA CHIOPODS. 247

OiiDEE II. — ARTICULATA.

The Avticulata, or Tcsticardiiiia, have the valves articulated by a liinge, usually
formed by teeth on the lower valve, fitting into sockets in the upj)er one. The
intestine ends blindly. On the inner surface of the ujiper valve a more or less compli-
cated calcareous loop, the object of which is to suppiort the arms. In tlie existing
forms this loop is usually quite simjile, but in some of the fossils it is very complicated,
portions being coiled in a sj)iral, which evidently supported all parts of the arms, so
that their extension from between the valves was impossible. In the living forms a
slight protrusion maybe occasionally seen.

Passing by the three extinct families, Production, Calceolid-e, and Oktiiid.e, we
reach first the family Rhvnciioxellid.e, of which forms are represented in the northern
seas. In these the arms are coiled in a sjiiral ; the shell is either free or anchored by
a peduncle, which passes through an opening in the beak of the larger valve. The
hinge line is either curved or straiglit, and the outer surface of the shell is impunctate.
Rhijnchonella psUtacea is a common form in the colder waters of the northern hemi-
sphere, from the Gulf of M;iine to P^urope. Other species are found in .Japan, New
Zealand, Fijis, etc.

The Spiriferid.e attained its greatest development in the paleozoic rocks, disap-
pearing in the Jurassic. In these forms the shells are unequal, have a straight hinge
line, while the support for the arms is coiled in two spirals, much like a watch-spring.
Occasionally these spirals bear hardened supports for the tentacles,
thus indicating that these parts could have but the slightest
motion.

The Terebratulid.e is the largest of the recent families. In
these forms the arms are not coiled in a spiral. The shell is punc-
tate and ventricose, the lower valve is perforated for the passage
of the peduncle, and the two valves are hinged together by two
teeth. On our New England coasts, TcreliratuUna septet itrionalis
is the most abundant, being brought up by tlie dredge from
a depth of only a few fathoms. Usually the specimens are en-
crusted with a yellow sponoe. In life the animal has considerable ''"'■ '■'■'-■ ~J\"'";:"<''"'a
powers of movement, raising itself at times so that it stands upright
upon its peduncle, or twisting itself around u])on the same support. In the more
northern waters of America the genus W(Mham!a is found, wliile the genus Thecid-
ium is found in the Mediterranean and tlie West Indies.

These forms are popularly known as lamp shells, their rounded shell, with its per-
forated beak, presenting no inconsiderable resemblance to the lamps used by the
ancients. The existing .species possess no inconsiderable vitality, and Professor Morse
has called attention to the striking fact that the ])Ower of the recent species to with-
stand a<lverse circumstances has a curious parallel in the history of the group, the
Liiiffu/a of the Potsdam sandstone being congeneric with the forms living in Japan
and the Caroliuas to-day.

J. S. KiNGSLEY.

248

LOWER INVERTEBRATES.

Branch VII. — MOLLUSCA.

With the possible exceptions of the insects and the birds, there is no group in the
animal kingdom which is such an universal favorite among all classes as the one now
under discussion. This is very natural; for the liard armor which they bear, and the
bright colors with which many of them are ornamented, renders them attractive, while
the comparative indestructibility of the same shells renders the care of a collection an
easy task. But while the collectors of the shells are many, the real students of the
animals are few, and even now, although these forms have been collected and studied
by concliologists for many years, a satisfactory classification is still desired.

The word Mollusca means soft, and it was ajiplied by Linne to a group of animals
embracing of the true molluscs only the naked forms, together with the hydroids,
echinoderms and annelids, while the shell-bearing molluscs were arranged as Testacea
in a section of his group of Vermes. Cuvier was the first to introduce order into the
group. His studies during the seven years spent as tutor on the Normandy coast
resulted in a classification of the Mollusca upon truly scientific grounds. The group,
as i-ecognized by him, embraced, besides the forms now admitted, the barnacles, the
ascidians, and the brachiopods, truly a heterogeneous assemblage. In after years the
Polyzoa were drawn in. The first of these groups to be separated were the barnacles,
which \\ere shown by Thomjison to be Ci'ustaceans in 1831. Then Kowalewsky, in
1865, described the embryology of the ascidians, from which it was apparent that they
had no relationshijis with the molluscs, but were rather to be classed with the verte-
brates, and lastly, the brachiopods were absolutely divorced from the grouj^, taking the
Polyzoa with them.

A concise definition of the Mollusca is impossible. Here, as elsewhere, nature
refuses to be bound by strict rules, and the best we can do is to form a general conceji-
tion which shall be true of the majority of forms, and which will, at the same time, be
loose enough to admit all. A mollusc, then, is a bilatei-ally synmietrical, unsegmcnted
animal, usually covered with a univalve or bivalve shell. It lias a ventral, muscular
portion (the foot) well developed ; a symmetrical nervous system, consisting of a

brain or supra-oesophageal ganglia, an ceso-
lihageal connnissure, and a secondary brain
beneath the throat. Most forms, in their
development, pass through a trochozoon
stage.

In some forms, esjiecially in the gastero-
pods, the bilateral symmetry of the body is
more or less obscured, owing to what niay

FIO. 253.-Diag,au> of mollusc; «, anus; I., biain. cere- ^^^ Called a tOrsion of the body, but, UCVer-
bral g.aiiKlion; f. foot; i, genital opening; ''.heart; theleSS, if we make allowauce for this twist-
i, pleural ganglion; /, liver; ??i, ntouth; n, Kidney; '

p, pedal ganglion; r, visceral ganglion. j„„^ jj ^.^J^ readily be traced. In the young,

the segmentation of the body is frequently evident, but it entirely disappears in the
adults, except among the chitons, where tlie elements of the shell and the gills are
metamerically repeated.

The foot is a muscular process on the lower surface of the body, which is highly

MOLLUSCS. 249

distinctive of most molluscs. In it one can frequently find three distinct portions in
serial order, known respectively as the propodium, (in front) ineso])odiuni, and nietapo-
dium. Occasionally lateral portions, epipodia, are developed. From the dorsal por-
tion of the body arises a fold of the body wall, the pallium, or mantle, which partially
or completely envelops the body. In some the two halves of the mantle may be dis-
tinct, while in others they are connected. This mantle plays no inconsiderable part
in the economy of the animal, for from it is developed the shell so characteristic of
most molluscs, and which deserves more than a passing mention.

The shell is largely composed of carbonate of lime, together with more or less animal
matter, the whole being secreted by the outer layer of the mantle. This shell is
entirely witliout blood-vessels, and is absolutely incapable of inter-
stitial growth. Such being the case, it is an interesting question
to decide how it increases in size. This is readily settled if we
burn a bit of some shell like that of the clam, to destroy the ani-
mal matter, and then break it across from the hinge to the margin
It will then be found that the shell is built up of a series of
layers, each of which, as we proceed inward, is larger than its pre-
decessor. The way in which the shell is formed by the mantle
explains this structure. When the animal is very small it secretes
a layer on the underside of the embryonic shell. With an increase
of growth another layer is laid down, but since the mantle is now
larger than it was before, this layer extends beyond the preceding
one. Other similar depositions follow, the result being that the
shell is thicker at the hinge than at the edge, while the outer
surface is marked with parallel lines, the edges of the successive
layers.

The structure of the shell presents many interesting iioints. *'iG. ^w. — Diagram-

' 1 • ,.1 ,1 matic section of sheU

it may be hard and opaque, like porcelam, iibrous, glassy, horny, showing the nu-thod

. . , . ^ , . . - 1 A of increase in thiclc-

or pearly, or nacreous, giving beautiiul iridescent colors. On ness iiming growth.

, , , , . , Tlie bl.acli spots indi-

mici'oscopic examination it is seen that tliese latter owe tlieir hues cate tiie successive
to minute undulations of the layers, and that they are ditfraction of 'the add'uctor'mus-
spectra similar to those now produced for physical researches by
fine rulings. The external color of shells is due to })igment deposited by the edge of
the mantle, which frequently bears the same pattern of ornamentation as does the
shell. Usually shells are covered with a horny external layer, the so-called epidermis,
which is likewise a jtroduct of the edge of the mantle. Its pui-pose is to protect the
shell from the corroding power of the water in which they live, or from other external
injury.

At some stage of growth almost all molluscs bear a shell, but with some it disap-
pears with growth. The shell may l)e univalve or l/ivalve, or in the case of that aber-
rant group, the chitons, it may be composed of eight pieces serially arranged. In the
first case it is usually coiled in a spiral, although a conical form is not rare. Among
the bivalves the two halves of the shell are nearly alike, though in some the similarity
is largely lost.

Turning now to the internal structure, we have first to take up the digestive tract.
This is always separated from the body cavity by proper walls. It begins with a
median mouth at the anterior end of tlie body, and terminates at the anus, which is
also primitively in the median line at the posterior end of the animal. The torsion

250

LOWER IN VEP, TEBRA TES.

which brings the vent in anotliei- position will lie discussed further on. The tlireo
divisions of the dio'estive tract, stomodeum, mesenteron and jiroctodeum are well devel-
ojied, the middle region being characterized by a very large liver.
Salivary glands are frequently present, emptying into the stomo-
deum, anil tlie same region frequently bears a lingual ribbon,
armed with teeth, for the comminution of food. This organ is
em])loyed to characterize the Cephalophora, one of the two great
divisions of the MoUusca, and will be described when treating of
that grou)).

The nervous system typically consists of two ganglia above
the oesophagus (cerebral) ; two at its sides (jileural) ; and two
beneath (pedal). These are connected by a ring of nervous
tissue. From eacli of the pedal ganglia arises a nerve cord whidi
traverses the length of the foot (the pedal nerve) while from the
pleural ganglia two similar cords arise, which also pass back-
ward, but at a higher level (the pleural commissures). These
terminate in a ganglion on either side, known indifferently as
Fig. 2.-)5,— Diagram cifner- the visceral or parieto-splanchiiic ganglion. Tliese two visceral

vous iuiatoinv of mollusc; ,. ^ t '^i i ,i ^i i i .i

a, abiiominai ganglion; ganglia are Connected with each other by a cord known as tlie
e,' eye';" ,f/rgiiif*"Vieu' visceral looj), in the middle of which is the abdomimd ganglion.
pefiai'''gai?giion ; "^'s, ' or- From the cerebral ganglia nerves go to the eyes, and primitively
ffvisceraTgaJigUon.'"'''' to the auditory Organ. An additional commissure on either side
connects the cerebral with the pedal ganglion.
The heart, which is situated dorsally, consists of a ventricle and one or two auri-
cles. It is always arterial, receiving the blood from the respiratory organs and
forcing it to all j^arts of the body. The circulation is not completely closed, the
blood for a portion of its course flowing through channels without proper walls.

Though the whole surface of the body has respiratory functions, special organs for
the aeration of the blood exist in the shape

of gills, or, less frequently, so-called lungs. ^..cs^ii^l

The gills are ciliated outgrowths from the
body, usually placed in the cavity of the
mantle between that envelope and the foot
or body wall. Each gill may be reduced
to a type called by Lankester a ctenidium. This, as its name indicates, is like a comb,
the back of the comb being the rhaehis or stalk, while the gill lamclUc correspond to
the teeth of the comb. In the rhaehis are two canals, one carrying tlie^blood to the
gill plates, there to be l)rought in contact with the water, the other returning it to the
heart. From this type most of the forms of gills can be derived.

All of the gills of Mollusca are not homologous, a fact first jiointed out by Spen-
o-el. This anatomist has shown that in the true or ty]iiral gills are normally jiaired
origans, one or more being found on either side of the body. These true gills receive
their nerves from the visceral loop of the nervous system, and he has also jiointed out
that at the base of each gill is a sense organ, the purpose of which is to test by smell
the quality of the water supjiliod to each gill. This olfactory organ is also innervated
from the same part of the nervous system as are the true gills. Other resjiiratory
organs exist in some ftvrms, but we liave a sure test of their homology in their rela-
tions to the nervous system and to the organs of smell.

Fig. 2S6. — Gill ot Sep'ui.

MOLLUSCS.

251

Fig. 257. — Xepliri'liuin of Unio; */, glandular pnition; 7), ex-
ternal opening; o, opening between {p) peric:irdiiun and
glaiulular portion of nepbridiiun; r, repi'oductive oritice; t,
non-glandular portion of nephridiuni; ;■, ventricle.

Lungs, which are ctxvities of the nuuitk' Ihietl with respiratory folds, occur only in
tlie puhnonate gasteropoils, where iliey will be de.seribed at length.

The renal organs, nephridia, or organs of 13oj:inus as they are frequently called
from the celebrated anatomist who
discovered them, are always present.
They are usually symmetrically dis-
posed, there being one on each side
of the body. Each nephridium con-
sists of a tube, the inner portion of
which communicates with a portion
of the body cavitj^, while the otlier
opens externally. In the interior
portion are well-developed glands,
which e.xcrete uric acid, while the
outer, non-glandular portion is merely
an afferent duct. That these iH'i)hridia are homologous with the segmental organs of
worms is more than possible, and the probability is strengthened by the fact that their
internal openings are ciliated, and that in many forms they serve for the extrusion of
the seminal, as well as for excretory, products.

Reproduction is here always a sexual operation, fission and budiling being un-
known. As a rule the two sexes are combined in the same individual, but numerous
marine gasteropods, and all cephalopods, are diojeious. The sexual glands are ])laced
on either side of the body, and either open through ducts of their own, or by means
of the nephridia, as mentioned above.

In all except the cephalopods there is a more or less com))licated metamorphosis
in passing from the egg to the adult. According to the amount of food-yolk, the seg-
mentation is regular or irregular, the result being a morula or mulberry-like mass.
Soon a portion invaginates, just as we may push in one side of a rubber ball, or, owing
to the presence of a great quantity of food-yolk, this process may be obscured. The
result, however, is in both cases the formation of a two-layered sac, the gastrula.
The mouth of the gastrula, the blastopore, soon closes more or less completely, and
from the middle portion is developed the foot, while the two ends correspond respec-
tively with the mouth and vent. Occasionally one of these openings ])ersists, but not
infrequently a new invagination takes place to form the openings, the in]>ushing of the
integument being always within the liinits of the blastopore. From the outer layer of
the gastrula is developed the e])idermal structures of the body, while the inner gives
rise to the middle division of the digestive tract. From this inner division cells are
also budded off between the two layers, formino" the mesolilastic tissues, and later one
or more spaces appear in this mesoblast, the body cavity. Further details of the
internal development may be found in sjiccial works, but for our purposes we need to
follow the changes in external form a little further.

At about the time of the invagination, a ]iortion of the outer surface develops a
circle of long hairs or cilia. This circle, wliich is known as the velum, embraces only
a small portion of the extei-ior, and since both mouth and anus, when formed, are
behind it, it follows that the area so circumscribed is pre-oral. Not infrequently a
single longer hair or flagelhim occupies the centre of the velar area, marking the differ-
entiation of the ectodermal Layer into nervous tissue, the future supra-oesophageal
ganglia. This stage is the trochosphere, and presents a close resemblance to the larva

252

L 0 WE It IN VEIi TEBRA TES.

Fig. 259. — Veligcr of Opistlio-
brancli; a, anus; /, foot; i,
Intestine; o, operculum; fc*,
velum.

of many worms, and esjjecially tlie lotiftTs. At this stage, or even earlier, another
important feature appears, the shell gland. This is at first an invagination on the side

of the body opposite the mouth, but

still outside the velar area. The gland

soon Haltens and begins to secrete the

shell, whicli at first appears as a single

delicate plate. Following the trocho-

sphere comes the stage known as the

veliger. The velar area is now a flat-
tened plate, fringed with cilia, and fre-
''' rf %;^f'?:1o^'7, quently expanded into lobes, while the
"""eiuin!' '^'" *^'''""'' rest of the body is greatly enlarged

in proportion. The foot is also more
prominent. With subsequent development the disj)roportion
between the velar area and the rest of tlie body increases
in all except a very few cases, as the pond-snail, Limncm.

Shells, more than any other objects of natural history, h;ive played a part as objects
of merchandise, and for the rarities, conchologists have in times past paid the most
fabulous prices. The following, copied from Tryon, may j^rove of intei'est to those
who have not yet caught the fever of shell-collecting : —

" Scalaria pretiosa., which can now be had for one or two dollars, was worth -IIUO
in 1735, and $'200 in 1701. Phasianella bulimo'ules, which also brought $100, can
now be purchased at from one to two dollars, or even less. In 1865 a great English
collection, that of Dennison, was sold by auction in London, and some extravagant
prices realized. Ci/prcea guttata brought -f liOO ; Ci/jnreajmiiceps, the same; Coitus
gloria-maris, aho $200; Conus ceryMS nearly 190; Conus cedonuUi (not a vevy rare
shell), $90 and $110; Comes omaictts, (also not rare), $60; Yoluta festiva, $S0 ;
Oiiiscia dennisonii, $90; Pholadomyia Candida, $65; Carinaria vitrea, (which ]Mont-
fort stated to be worth $600), brought $50. The very rare Pleurotoma quoijaiia
brought in London, in 1872, $125. In 1876 the Roters van Leimep collection was
sold, including: Valuta JHiionia, $50; Mitra heldieri, $40; Spondylus reglus, $30,
etc. For this same Spondylus regius Professor Richard had previously paid several
thousand francs. Voluta junonia has always been considered a rare species, and
dealers have obtained as much as forty pounds sterling for it. . . . Cypnva
unibilicata has been sold for thirty pounds, and may now be had for one pound. The
Boston Society of Natural History possesses an Argonauta argo, or paper nautilus
shell, which is said to have been purchased by the gentleman who jjresented it to that
society, for $500. It is a common species, and the only reason of the greater valua-
tion of this specimen is that its diameter is about two or three inches greater tlian any
other individual known to naturalists."

Class I. — ACEPHALA.

This group of the molluscs has been burdened with a large ntimber of names.
Among them we find Conchifera, Endocephala, Li|)Ocephala, Lamellibranchiuta, and
Pelecypoda, as well as the older, and consequently ])referable, designation adopted
here. The group will readily be recogni/.ed by all umlcr the popular designation of
bivalve molluscs. In this more familiar name is embodied one of the most character-

MOLLUSCS.

253

istic features of these forms, — .1 shell diviiled into halves, one on either side of the
body. This bilateral symmetry pervades the whole organism, and frequently one
side is almost an exact repetition of the other. Just inside the shell is found the
fleshy mantle, which, like the shell it secretes, forms a flap on either side of the body.
In these bivalves this pallium, or mantle, acquires a great development, and not infre-
quently its edges are joined together, so that the rest of the animal is enveloped, as it
were, in a bag. Still the bag is never completely closed ; at the front end a small

Fig. 260. — Diagram of anatomy of a clam (7v/;/a); a, anterior adductor; b, auricle; c, excurreiit
siplional tube; e. incurrent siplional tube; /, foot; r/, gills; i, intestine; m, mouth; /;, posterior
retractor; r. retractor of foot; t, labial pal[)i; v, ventricle of heart.

hole is left for the protrusion of the foot, while, at the o))i)Osite extremity, means is
afforded for the entrance of water, bringing food and o.xygen to the animal, and also
for the escape of the same fluid, bearing away the waste products of respiration and
digestion. Not infrequently this posterior opening becomes divided into two tubes,
which sometimes can be extended a long distance from the shell. This is known as
the siphon, and will readily be recognized by most people in the 'head' of the clam.
Head it certainly is not, for it is at exactly the opposite end of the body from where
the head should be. These tubes, which are, in reality, but expansions of the mantle,
are very contractile, and each tube has its own function. The lower one (the one fur-
thest from the hinge of the shell) is for the incurrent stream, while from the other
tlie water which has played its jiart in the economy of the animal is discharged. In
other forms there is no siphon, and in still others
the two halves of the mantle are entirely free
from each other.

The mantle joins the body near the hinge
line, and between the two hang down the gills,
to which we shall again recur. From the lower
side of the body proceeds the foot, which in some
forms is well developed, even proving an organ
of locomotion of no mean capacities, while in
others, like the oyster, the foot lias nearly, or even
entirely, disappeared. Near the extremity of the foot in the adults of some species,
and the young of others, is a gland, the function of which is to secrete the byssus.
This is a l)undle of fibres, more or less closely united, Ijy which the animal attaches
itself. The byssus can be cast off by the animal when desired, and a new one formed
at pleasure.

The mouth, which is at the oi)posite end of the body from that at which the siphon

Fig 261. — Jtussel with byssal threads.

254

L 0 WER IN VER TEBRA TES.

Fig. i&i. ■

-L)i;igram showing the devehipmeiit of the
giUs of a laiiiellibranch.

arises, bears, at the sides, a pair of leaf-like or tentacular folds, the labial palpi, the
fiiiietion of which is to direct and conduct currents of water to the mouth, the cilia
with which they are covered aiding greatly in this respect. It has been suggested
that these paljii represent the velum of the larva, but no known facts of embryology
confirm this view. They are, in reality, the greatly expanded upper and lower lips.

The alimentary canal always traverses the whole length of the body, terminating
m a vent at the posterior end. Usually its course is much contorted, the intestine, in
some forms, passing through the ventricle of the heart. The Q?sophagus is short, and
communicates with a more or less spherical stomach, into which a voluminous paired
liver pours its secretion. The intestine is very long and convoluted. No organs of mas-
tication are present, and, if we make one pos-
sible exception, nothing that can be compared
to the lingual ribbon of other molluscs. This
excejition is the crystalline style. This is a
transparent elastic rod, of unknown functions,
which lies in a j^ouch arising from the stom-
ach. Whether it be a I'epresentative of the
odontojihore is very uncertain.

The heart always consists of a median
ventricle, which forces the blood to all parts
of the body, and two auricles, one on either
side, which receive the blood from the gills
and pour it into the ventricle. The gills
possess a very complicated structure, but one which can without much difficulty be
reduced to a simple type. Of these organs there are
usually two on either side. Embryology shows us that
each of these gills is primitively made up of a series of
little tubes running down from the body wall. These
tubes then turn and grow back until they reach the inner
surface of the mantle, as shown in the adjacent figures.
The filamentary condition persists in some acephals, but
in others the adjacent filaments become united so that a
broad lamellar gill (whence the name Lamellibi-anchiata)
is the result. In some forms this union is produced by
bunches of hooked cilia on the sides of the tube, while
in others the walls of the branchial filaments become
solidly grown together. The blood from all jiaits of the
body gathei-s in a large tube at the base of the gills;
thence it ])asses down through one half of the little tubes,
and up in the other, to another vessel, whence it is con-
veyed to the heart. During this passage it is brought in
contact -ivith the water, dischargitig its carbonic acid, and taking a new sujiply of
oxygen.

The way in which the water is brought into the cavity of the mantle, and m con-
tact with the sill, is very interesting. The oills, and for that matter the whole inner
surface of the mantle cavity, are covered by innunieriible little hains, or cilia, wliicli,
by their constant motion (always in one direction) create currents in the water, draw-
ing it in through the iiicurrent siphon, passing it over the gills, around to the mouth,

Fig. 2C.'.!. — Section through gill
filaments of Mi/lilns. showing
the hooUeil cilia which fasten
them together.

MOLLUSCS.

255

and then out through the fxcuneiit opuniiig. Singly these cilia are very weak, but
together they exercise a great deal of force. Many experiments liave been tried by
cutting out a piece of the gill, placing it on a flat surface, and covering it with a
Aveight. The amount which will be moved by these minute lashes, under these circum-
stances, is almost beyond belief, the motion in one instance being six millimetres a
minute.

Tlie excretory organs are paired, and communicate internally witli the cavity (peri-
cardium) surrounding the lieart. The nervous system consists of three pairs of gang-
lia, a cerebral or supraceso-
phageal, a pedal, and a pa-
rieto-splanchnic ])air. The
arrangement of these shows
many minor variations.
Normal]}-, the first pair is
situate above the oesophagus,
but they may be brought be-
neath that tube, occupying
a position just outside the
pedal ganglia, which are, as
their name implies, situate
in the foot. The last pair
are placed just beneath the
posterior adductors. The
two latter pairs are con-
nected with the first by
double cords. Besides the
sense of touch, organs of
smell, hearing, and sight are
developed in most of the
group. The olfactory or-
gans are situated upon the
parieto - splanchnic ganglia,
the auditory organs near the
ganglia in the foot, while the
eyes are very variable in
position. The organs of
smell are merely patches of
elongated epidermal cells,
strictly homologous with
similar organs in other mol-
luscs. The ears are small
sacs lined with cilia, each
containing a single otolith, which, by its vibration against the cilia, coineys the seiis;v
tion to the nervous system. The eyes may be found either upon the edges of the
mantle or upon the tip of the sii)hon. In some forms like Spomh/lus, Fecten, Ifactm,
etc., these eyes on the edge of the mantle are well developed, and, like those of On-
chidiuin, which will be mentioned in a succeeding ]jage, are similar to those of verte-
brates, in that the nerve fibres penetrate the retinal body, and distribute themselves

Fig. 264. — Diag'-am of AnnfJonta: «, anus; 6, cerebro-viscer.al connective;
/«•, cerebro-pleui-al ganglia; c, gill; rl, mantle; e, posterior aildnctur; ax,
ex'ernal lamella of inner gill; /, foot; q, genital opening; in, inner
lamella of inner gill; /, visceral (parieto-spianclinic) ganglia; //), labial
palpi; m, mouth; p, peiial ganglia; r, renal opening.

256

L 0 WER IN VER TEBRA TES.

on the outer einls of the rods ami cones. In the siplional eyes found in Solen, etc., we
have the merest apology for a visual organ.

The se.xes of the acephals are usually separate, though in rare instances they are
united in the same individual. Tlie genital glands are on either side of the body, and
empty by paired duets. The eggs are either cast free in the water or are retained for
a time between the lamellae of the gills of the parent. The veliger presents a promi-
nent difference from that of gasteropods, in that the primitively simple shell soon
becomes bivalve. The peculiar larval form known as glochidium will be mentioned
in connection with the Unionidae farther on.

Lastly, in our general account, comes the shell, which occupies so important a place
in existing schemes of classification, and with it may be mentioned some of the fea-
tures of anatomy which have been neglected in the preceding page. On examining
the outer surface of any bivalve shell one notes the lines of growth concentrically
arranued. These have as a centre an elevated portion of the shell known as the umbo,
the position of which marks the dorsal border. Usually this umbo points towards one
end of the shell, which may thus be recognized as the anterior. Having these land-
marks, we can readily decide the question of right and left. At the dorsal margin,
where the two valves join, is the hinge line, and just in front of the umbo is fi'e-
quently a distinct area, half on each shell, the lunule.

Now for the mechanism which opens and closes the valves. The closure is
effected by one or two transverse muscles (adductors they are called) which iiass from
one shell to the other, and by their contraction the two valves are api>roximated. No
divaricators exist, but instead the valves are separated, the moment the muscles are
relaxed, by moans of an elastic ligament. This ligament may be either extei-nal or
internal. In the former case, as shown in Fig. '205 A., the ligament connects the two
valves, and by its contraction spreads them. In the either (Fig. 265 B.,) the internal
liuament is placed between two portions of the shell, so that when closed it is com-
pressed, but u])on relaxation of the muscles the elasticity and expansion of the
ligament forces the valves apart.

On the internal surface of the shell we also find certain features which are made
prominent in systematic work. Just where the two valves join together is the hinge,

usually provided with projections
and depressions, forming what are
known as teeth. Those in the cen-
tre are known as the cardinal, and
those frequently present at the sides
as the lateral teeth. Near the
hinge line, but on the inner, con-
cave surface, will be found one or
two ajiproximately oval marks, the
imjiressions produced by the attach-
ment of the adductor muscles.
When only one muscle is jiresent,
it is morphologically the posterior
one. Usually close to these may
be seen other similar but smaller
scars, markino- the spots where the muscles of the foot had their origin. Going around
the margin of the shell is a line, more or less distinct, called the pallial line, which

Fig. 2G5.-

- Diagram shomng llie hinge ligament, internal and
external; ^ ligament; m, muscle.

MOLLUSCS.

257

marks tlio limit of the tliiekened t'dgo of the mantle, and in one large group of shells
a poi-tion of the pallial line makes a re-entrant angle. This is the jsallial sinus and is
found only in liivalves with a siphon,
where it marks the 2:>lac'e of attachment
of the muscles of that organ.

Tlie classification of the acejihalous
mollusca is still in a very unsatisfactory
condition. In the system of Lamarck
the group was divided into two sub-
classes, based upon the number of ad-
ductor muscles, those in Avhich only one
of these muscles was present forming
the Monomyaria, while those with two
were called Dimyaria. Woodward, who
wrote one of the most valuable manuals

of COnchology which has as yet ap- fig. 26C. — Iimer surface of left valve of C//</ierea.rt, impres-

f^*^ "^ ^ sion of auterior adductor; f, cardinal tooth of binge; A,

peared, used the presence or absence hinge ligament; ;, pallial line; p, posterior adductor; s,

,. . , „-,... pallial sintis; ^lateral teeth of hinge; w, umbo; a-, lunule.

01 Siphons as a means or division, those

where no sijihon was formed licing the Asijihonida, the others forming the Siphonida.
The Siplionid:i in turn were subdivided, according to the presence or absence of a pal-
lial sinus, into the Shiup;illialia and the Integropalliala, respectively. With each of
these systems many grave faults may be found, and hence, for our ]nirpose we will
divide the Acephals directly into families, without the intervention of sub-classes and
orders, and other intermediate divisions.

In economic importance the Ostreid.e, the oyster family, stands pre-eminently
first. The characters of the family, taken in its older and broader sense, are as fol-
lows: The two valves of the shell are une(|u;d, the hinge is without teeth, and, as a
rule, tlie single adductor is nearly median in its position. The two halves of the
mantle are free from each other, and the borders are fringed with small tentacles, and
the foot is rudimentary or even entirely absent.

The genus Ostrea has a shell so irregular that specific limits are very poorly
defined. The left valve, which is attached to some submerged object, is hollowed out
to receive the body, while the upper right valve is nearly flat. With us Americans,
Ostrea virginiana is the important form, and to it most of the succeeding account
applies. In Europe the species which form the bulk of those eaten are 0. edulis and
0. aiujulatK.

Ostrea inrc/iiiiana extends, on our Atlantic coast, from the Gulf of St. Lawrence
to the Gulf of Mexico. In the former region the oysters are found from the Bay of
Chaleur to Prince Edward's Island. The beds are small and in many ]ilaces seem to be
decreasing. The oysters found here are usually large. These beds are separated
from the nearest natur:il living beds to the south, liy a thousand miles of coast line,
but between these points evidence is alnindaiit that in former times the gaj) was far
less, for remains of extinct beds are found all along the coast, from IMonnt Desert
Island to Cape Cod. At Damariscotta, Maine, was once a large bed which furnished
the Indians with the means of many a feast. Here, year after year thev came, and
with the refuse shells they formed huge heaps which to-day are the delight of the
archaeologist. The oysters in these "kjokkenmoddings" fa Danish term meaning
heaps of kitchen refuse) were of enormous size, one having been found at Damaris-
VOL. I. — 17

258

LOWER INVEll TEBRA TES.

cott;i wliicli measnvcd fifteen inches in length, lieniains nf other beds, and indications
of still others in the shape of kjokkeninoddings, are abuiidant along the coast, at l^ort-
land, Ilarpswell, and j)oints in Massachusetts.

It seems that most of these beds, north of Cape Cod, have become extinct since
the first settlement of the country. The old records tell of beds in the Mystic and
the Charles Rivers, near Boston, which were well known to the early settlers, but all
trace of them is now lost. The same is true of many other places. What was the
cause of this extinction is not easy to decide. Professor Verrill, who has taken into
consideration the facts afforded by the past and present distril^ution of other mol-
luscs, is inclined to attribute it to a climatic change ; others to over-fishing, pollution
of the waters, etc.

South of Cape Cod the oystei- still flourishes in its native vigor, and an enumera-
tion of the places with extensive beds would be about equivalent to giving a catalogue
of the shore towns from Buzzard's Bay to Texas. In Long Island Sound, and on the
Jersey coast, besides the supply of natives, large numbers are transported from the
Chesapeake. These latter are brought in the shape of small (seed) oysters, and are
scattered in suitable situations, where they increase in size. When large they are
taken up and sent to the market. The profits on this operation are said to be large.
It is in Chesapeake B.ay, and its various creeks and sounds, that the oyster business
reaches its greatest development, and where the study of the various economic and
scientific problems connected therewith, have received the greatest attention, an
account of which will not be out of place here.

In our American oyster the sexes are sejiarate, \mt\^ thanks t<i the labors of Dr. W.

K. Brooks and Mr. J. A. Ryder, we now have a pretty
complete knowledge of the life history of this valuable
form. The eggs are fertilized after leaving the parent,
and undergo their development in the water. The de-
velopment is normal and direct. After the formation of
the velum the young oyster swims freely through the
water, during which time the shell and tlie internal
organs are being gradually develoj)ed. In a few days
this free life ceases, and the young oyster attaches itself
to some submerged object. The way in which attach-
ment is effected is at first by the rudimentary shell of
the left valve, and subsequently, as lime salts are de-
posited in the shell, they serve to unite the young oyster
more firndy to the point of support. When first attached, the young oysters are
termed 'spat;' when large enough for transplanting, 'seed.'

The life of the oyster depends upon many things, the most prominent being the
location. At the time the embryos are to be converted into spat they need some solid
object to which to attach themselves. On the natural beds this is found on the shells
of other oysters and on rocks, but where artificial beds are formed it is customary to
throw down old shells. In artificial propagation 'collectors' of earthenware, slate, etc.,
are used. The young oyster needs plenty of water and food, and also needs protection
from mud, which would soon smother them. The food consists almost wholly of mi-
croscopic animals and plants.

Many experiments have been tried to raise oysters in confinement, but mitil i-ecently
they have not been successful. The great trouble has been in keeping the young alive.

Fig. 2G7. — Youns oyster.

MOLLUSCS. 259

Mr. J. A. Ryder solved the iiroWein in tlie following- inMiiiier. An artificial pond was
formed, and filled with salt water, which was filtered thi'ough sand, and all connection
with the ocean was by means of a ditch interruj)ted by a bank of sand. This i)ermitted
a slight change of Avatcr with eaeli tide, but j)reventcd the entrance of injurious forms
and tlie exit of the young Itefore their transformation into s]>at. In the pond were
placed numerous collectors, to which the sjiat could attach itself; and after the _young
shells had attained sufficient size to take care of themsehes, these collectors, with their
Tiiolluscan load, could be transferred to the beds in the adjacent sounds. By this
])rocess the period of greatest mortality is passed in comparative safety, an<l the
result of Mr. Ryder's labors will doubtless be to greatly increase the supply of this
delicious bivalve.

The oysters are taken from the beds by rakes, tongs, and dredges; the names of
which indicate their general appearance. When l)rought to the shore, some are .sent
to market, while others are ' shocked,' and sold as solid meats. The extent of the
oyster industry in the United States can be seen from the following figures, extracted
from the census of 1880. The business gives employment to over fifty thousand per-
sons and over four thousand vessels, and involves an investment of over ten million
dollars. The number of bushels of oysters produced is over twenty millions, and, at
first hand these sell for over thirteen millions of dollars. Eacl) State has its own laws
and regulations regarding its shell-fisheries, and in Maryland and Virginia an ovster-
police is maintained, to prevent irregular fishing and depredations upon the beds.

Our east-coast oyster has been described under four sjiecific names, virc/imana, vir-
i/inica, borealis, and canadensis, but all have been shown to lie vario'ties of one and
the same form. The average length of those brought to market is, jierhaj^s, four to
six inches, but larger ones are not uncommon ; but how much credence is to be given
to the following quotation from the "Mobile [Alabama] Register," of A])ril, 1840,
taken from "Ingersoirs Monograjih of the Oyster Industry,'' is a question. The quo-
tation runs: "The large oyster taken by Xavier Francois, while oystering on Monday
last, was brought up from the wharf, on a dray, last evening. An oyster measuring
three feet one inch in length, and twenty-three and a half inches acn-oss the widest
part of it, is a curiosity."

On our western coast two s]K'cies of oyster are eaten. Of these O. conchophila,
of California, is small, while the O. lurida, from Shoalwater Bay, Washington Terri-
tory, is much larger and better. Still a large jiroportion of the trade is supplied by
oysters shipped from the Atlantic coast. In 'Europe the oysters most eaten are 0.
anffulata and 0. edidis. Of these the former has the sexes separate, while the latter
is hermajihrodite. Sjiace will not allow a, detailed account of the many and successful
trials that have been made in the propagation of these forms, and we can only refer to
the green oysters so highly prized by the Parisian epicures. Many theories have been
proposed to account for the color, — such as the presence of copper, etc., — but it now
seems proliable that it is due to the effect of the food, the chlorophyl of the vegetable
lood being transferred to the blood, or some peculiarity in other objects eaten affect-
ing the liver. The British market is now largely supplied from the Tainted States,
the American oysters being much larger, and better flavored than those of European
seas. The trade amounts to about half a million dollars yearly.

Edible oysters are found at the Cape of Good Hope, in Australia, Japan, and else-
where. The O. talienwanensis, of Japan, occasionally measures three feet in length.
Other forms which deserve mention are the species of the sub-genus Alectryonia, which

260

LOWER INVERTEBRATES.

are found attached to the roots of mangrove and other trees, in the warmer seas of
the world. The oysters appeared in the carboniferous age, and have persisted until
the present time. Among the fossil forms closely allied to Ostrea
may be mentioned the genera Gri/phcea and Uxoffi/ra, in which
the shell attained great thickness and
weight.

The genus Anomia, though pos-
sessing but little economic imijortance,
„ „ „ is especially interesting from the fact

Fig. 268. — A ery yoiuig ^ . .

Aiiomia, showing that for a lono- time it was supposed

the byssal notch ^ ^ -^

not yet convei-ted to form a Connecting link between the

hito a foramen. .

brachiopods and the molluscs. Like
niany of tho.se forms it lived .attached to rocks or shells
by means of a tied uncle, which perforated one of the ViG.2m.—Anmnia epUippium, ^hovvag

bvssiis

vjilves of the shell. Could the correspondence be

stronger? Wlien the mode of growth was studied it was found th.at the tW(j were en-
tirely different. Anomia, in its early stages, spins a byssus, by which it attaches itself
to some foreign object. As the shell increases in size, the byssus interferes with the
growth of one of the valves, producing a notch in its margin. As growth contimies,
the two edges of the notch close around the byssus, resulting in the perforation.
As this closure occurs at an early stage of development, the foramen produced is
close to the hinge, thus strengthening the resemblance to the similar opening in the
brachiopods, though, as will be readily seen, there is no homology between them.

Besides the perforation of one valve for the byssus,
the genus Anomia is characterized by having the two
valves unequal, one being larger and convex, while the
other (the perfor.ated one) is flattened, or even concave,
according to thi' location on which it settled. The
hinge is without teeth. The species vary greatly, so
that it is very difficult to define them. On our coasts
two forms are commonly found, A. c/labra and A. acti-
leata, the former being essentially a southern, the latter
a northern form. Anomia glabra is especially com-
mon on oysters. In color it is glistening white or
yellow, and hence has received the names silver shell
or gold shell. A. aculeata is usually sj^iny or scaly.
It is more varied in its places of attachment, rocks, shells, and large algae forming-
favorite localities. TJiis is very closely allied to the Anomia eplivppiuni of Europe.
On the coasts of California occurs A. pernoides.

Placim.a is a genus with tliin shells, in which no byssus is formed. The valves are
nearly equal, and the species inhabit sandy shores. The species are inhabitants of the
Indo-Pacific Ocean.

Tlie family Peotinid^, or scallops, comes next in order. Here tlie valves may be
similar or different, wliile the anterior and posterior halves of each valve are nearly
alike. The hinge is prolonged on each side of tlie umbo into an e.ar-like process.
The borders of tlie mantle are free, and frequently tliey bear a number of brightly
colored eyes, which have been made a subject of study by Mr. Ilolmaii Peck. A
single adductor is present, and the gill filaments are free, showing as a jiermanent

Fra. 270. — Anomia tilahra.

MOLLUSCS.

261

Fig. 271. —Placuna sella.

structure, a condition characteristic of the young of the higher forms. The foot is

small, and frequently spins a byssns, hy which the animal attaches itself.
The typical genus of the

fainily is Pecten, in which the

regular shell is iisually ribbed,

the lines radiating from the

umbo. The anterior ears of

the shell are the larger. In

older times species of this

genus were known as " pil-
grims' shells," from the fact

that for some unknown reason

the jiilgrims of the middle ages

were wont to ornament their

clotliing with these shells. So

prevalent was the practice,

that when, in tlie early days of

science, it was adduced as a

proof of the biblical record of

the flood that fossil shells were

found in the Alps ; the reply was made by sceptics, that tliese were merely shells

dropped by pilgrims returning from Palestine.

The common scallo]) of the southern shores of New England is known in scientific

terminology as Pecten irradians. It lives
in shallow places, among the eel-grass, and
swims away at the slightest alarm. This
swimming, which is somewhat rare among
Ijivalve molluscs, is effected by rai^idly open-
ing and closing the valves of the shell, the
result being a sub-aqiwtic flight in a buck-
ward direction. In color tliis .species varies
considerably, but tlie flat val^'e is always
lighter than the other, being often white.
The otlier valve may be reddish, orange,
I inrplish, or mottled «'ith two of these colors.
The eyes, upon the edge of the mantle, are
siher or bluish, and are thirty or more in
number. Tliis is the scallop of the markets,
and is highly jirized by some, though its
sweeti.sh tnste makes it unpleasant to others,
iroductive of nausea. Only the adductor

Fig. 272. — Pecteii irradians, scallop.

while some find it actually unhe.-iltliy, ami
muscle is eaten.

North of Cape Cod this sjiecies is replaced by two larger ones, P. i.sl/nuh'cits and
P. tenincostatus, neither of which are of much economic importance. In Europe the
scallop (P. maxi/nus) and the quin (P. opercnlaris) are extensively eaten. Other
species, nearly two hundred in number, are found in all the seas of the world.

In Ziiy-ia the shell is ob]i(]uely oval, and gapes anteriorly. Tlie hinge is straight,
toothless, and the ears are small. The border of the mantle is fringed with long cirri.

262

LOWER INVERTEBRATES.

but the eyes have not yet been discovered. Whether or no they are really absent has
not yet been decided, but the recent investigations of Dr. Benjamin Sharp show that
lio-ht-perceiving organs exist in many forms where their presence was not previously
suspected, and so it may be here. Lima Jdans, the species figured, swims with great
ease, and in the same manner as do the scallops. It also spins a byssus, and the adults
not infrequently build a rude nest or burrow, by cementing togetlier bits of coj-alline,
(shells, and sand. "The species of Lima usually live quietly at the bottom, with the
valves widely extended, and thrown flat back, like the wings of certain butterflies
when basking in the sun ; but when disturbed, they start up, flap their light valves, and

, move throutih the water

yi0^—-\-X I / by a succession of sud-

^>^_3^^-^ »-]/-% \a^ den jerks. The cause

C- ^ ^ \v ' ^^ alarm over, they

, '^ "*" , bring themselves to an

^ '' ^ ^ anchor by means of

their provisional bys-
sus, which they seem
to fix with nnich care
and attention, previ-
ously exploring every
part of the .surface with
their singular, leech-
like foot."*"

The species of Sjam-
(lylus are known as
thorny oysters. The
unequal valves are usu-
ally armed M'ith spines,
which not infrequently
are very long and flat.
The right valve is the
largest, and is attached
at the beak, the hinge
ligament is internal,
and the hinge is pro-
vided with two teeth in either valve. By the process of growth, the hinge area of
the lower valve becomes converted into a triangular space furrowed down the
centre by the groove for the hinge ligament. Slight ears are present at the hinge line.
The ocelli on the margin of the mantle are numerous. The species are all inhabitants
of tropical and sub-tropical seas. In the West Indies occurs *S^. americana. ^ S. c/adero-
pus, of the Mediterranean, is said to produce iiearls. Most noted of all is the SiMv-
dylus rerjvus of the East Indies, which is classed among the rare shells. In times past
perfect specimens have brought immense prices, and no longer ago than 1876 a specimen
sold for thii'ty-six dollars. The long and delicate spines are so easily broken that per-
fect specimens are com])ai-atively rare.

The AvicuLiD^ is the family of the true pearl oysters, and although many other
molluscs jn-oduce j.earls valued as ornaments, it is to this family that the world owes
the largest ])roi)ortion of these so-called precious stones. The family is characterized

-Lima Mans in its nest.

MOLLUSCS.

263

by having the hinge line strniglit, and produced on either side into wing-like ears.
The valves, which are very oblique (their axis being at a considerable angle with the
hinge line) have a foliaceous texture, and are lined on the interior with mother-of-
pearl, giving them an iridescent ajipearance. These rainbow hues are due to the fact
that the surface is covered by nunute lines, which produce diffraction spectra. Soon
after the fact was discovered that fine lines produced this ajipearance in the mother-
of-pearl, some ingenious person applied tlie same method in the arts, and at one time
buttons, etc., were made from steel, which had this same iridescent appearance pro-
duced by engraving microscopic lines upon the surface. Lately this phenomenon of
diffraction has been turned to a scientific use, and to-day glass or speculum metal.

Fir.. 274. — Sponilyhis rcf/iiis, thorny oyster.

ruled with very fine lines, is used to produce the spectrum studied in spectroscopic
analysis.

The hinge of the shell is without teeth, or with these elements obscure, while the
ligament is partly internal. Tlie shells gape in front, but are closed behind. The
small foot spins a byssus ; the mantle margins are free throughout their extent, and two
adductor muscles are present. Of these the posterior is large, the anterior small and
placed under the beaks of the shell, producing an almost imperceptible scar upon the
inner surface. All the species are from the warmer waters of the globe.

In Avicula there is a single cartilage pit, and the hinge is furnished with two
teeth; the right valve has a notch near the anterior ear for the passage of the byssus.
Meleagrina lacks the hinge teeth, and the ears of the hinge line are small. The most
prominent species is 31. mni-r/ardtlferd, the true pearl oyster, which has an extensive
distribution, being found in Madagascar, the Persian Gulf, Ceylon, Australia, Philip-
pine Islands, the South Sea Islands, Panama, West Indies, etc. The pearl fishery is
carried on at many points, but the finest pearls are said to come from the islands of
Bahrein, Karak, and Corgo in the Persian Gulf. The chief fisheries are those of

264

LOWER INVERTEBRATES.

Ceylon. The oriental pearl oyster is much larger than the American form, the average
diameter being, perhaijs, nine inches, while specimens a foot across are not very rare.
The principal locality of the Ceylon fishery is on a bank about ten or twelve miles off
the north shore of the island.

Each night, at about ten o'clock, during February, March and April, a fleet of
small vessels starts from Condatchy and Arip|)o, Ijouud for the oyster banks, which are
about twenty miles long. Arrived on the ground, the fishing beghis. Each Ijoat has
a crew of twenty-three, ten of whom are divers, and these last are divided into two
gangs of five each, one lot resting while the others are Ik'Iow. The a%erage dejith of

the bed is between nine and ten fathoms, and it nowhere exceeds thirteen. Each
diver has a rope weighted at the lower end by a stone weighing about thirty pounds,
and just above this is a loo]) for the foot of the diver, while a large net-work basket
is fastened above. The diver, placing his foot in the loop, is rapidly lowered to the
bottom, and there, working as fast as possible, he fills his basket with the oysters, and
then, giving the signal, lie, together with the weight and the basket of oysters, is
quickly hauled to the surface. Incredible tales are told of the length of time that
these divers can remain beneath the surface, but no well-authenticated case exists
where one remained longer than eighty seconds, and but few can remain longer than
a full minute.

When the boat is filled (which requires from fifteen to thirty thousand oysters) it
returns to the shore, and the cargo is placed in an, earthen bin, with walls about two

MOLLUSCS.

265

feet high, and then left to die mid decompose. "When tlie flcsli is ])retty thoroughly
disintegrated, it is waslied away with water, great care being taken that none of the
pearls loose in the flesh are lost. When the washing is concluded, the shells them-
selves are examined for jiearls, which may be attached to the interior of the valves.
The loose pearls are the most valuable, as they are round and more apt to be free
from defects. Those attached to the shells have to be removed hj clijiping, and as
one side is thus defective, they can only be used in settings. For over two thousand
years this pearl fishery has been carried on in this place, and the result is that the shell
heaps are perfectly enormous, miles of territory being buried to an average depth of
about four feet.

Concerning the fisliery in other localities but little has been written, although
Panama, the island of Margarita, and the Sulu islands produce considerable numbers.
The best pearls are usually about the size of a jiea, but the largest known was two
inches in length and four in circumference, and weighed three and three fourths
ounces troy weight.

Tlie pearl oyster is valued not only for the jiearls which it produces, but for
the mother-of-2:)earl as well. Of this there are three varieties recognized in the
trade, the best of which are the silver-lipjied, from the South Seas ; next come the
blaek-lipjjed, from Manilla and Ceylon ; and lastlj' those known as bullock shells, from
Panama, etc. These last are smaller and thicker than the others. Reliable statistics
of the amount of the trade are difficult to obtain, but its extent may be seen from the
fact that Great Britain uses annually about three thousand tons, valued at half a mil-
lion dollars. Mother-of-]iearl is used for inlaj'ing, knife handles, etc., but the greatest
consumption is in the manufacture of pearl buttons.

Mother-of-pearl is but the nacreous shell of the pearl oyster, which has an iridescent
appearance, due to the fine stria- caused by the undulating layers of which it is com-
posed. The true ])earls are, like the shell itself, produced liy the mantle, and owe
their beauty to the same cause. They are, however, abnormal products, caused by
the deposition of the nacre around some foreign object. This nticleus may be a bit of
sand, a parasite, or some similar ob-
ject, but it is said that usually it is
an egg which has failed to develoji
properly. Other forms than the
pearl oyster {Meleagrina) form
pearls of value, while almost all
bivalves occasionally secrete simi-
lar bodies ; but, owing to the fact
that these partake of the nature of
the shell, they have not the l)eauty
of those produced by molluscs with
nacreous interiors. Of some of
these other peai-ls we shall have
occasion to speak further along
when treating of some of the other

tamiues. p^^^ t,6. — Malleus nUgarls, Iiainmer shell.

The genus Malleus includes the
hammer shells. With their long, winged hinge, and their still longer valves at right
angles to the hinge, they well deserve both their conunon and their scientific names.

266 LOWER IXVERTKBRATES.

In the young stage they closely resemble the genus Aoicula, even to havmg the
notch in the right valve for the byssus ; but, as they grow olde)-, tlie body of the shell
becomes more ribbon-like, its edges grow wavy, and at last the shell takes on the adult
characters. Several species are known, all inhabitants of the eastern seas.

In Perna, which in general appearance resembles Avicula, the cartilage grooves are
several in number, arranged at right angles to the line of the hinge. In some of the
fossils of the tertiar\' age, the pearly layer lining tlie shell is an inch in thickness.

The family Mvtilid.e embraces the mussels, in which the two valves of the shell
are equal, convex, and covered with a thick ejndermis. Tlie hinge is weak, without
teeth, and with the ligament internal; the posterior muscle is large, the anterior small;
the foot is cylindrical and grooved, and secretes a byssus. The mantle is mostly free,
but at the ])osterior end the margins unite to form a rudimentary syphon with fringed
margins. Most of the species are marine, but a few live in fresh water.

31i/f.iliitt^ the typical genus, has a world-wide distribution, and is represented on the
northern shores of Ixitli <'()iitinents by the common mussel, Mytilus eclulis. On our east

coast this extends as far south as the Carolinas, to
San Francisco on the west coast, while on the
eastern continent it is found in Great Britain and
the Mediterranean and in China and Japan. In
color the specimens from exposed situations are
dark-brown or bluish-black, while in more shel-
, ,. , tered localities one frequently finds specimens of

riG. 2u. — J///r/7«.s' ef/?f//s, coiiimoii mussel. . , , ^ •^ _ ^ ^

a light, pellucid, olive-green, striped with darker,
or occasionally all banding may be absent. These mussels grow in innnense quan-
tities in certain situations, rocks, piles, etc., being covered with a thick matting, each
individual of which is anchored by its silken, yellow byssus. In Europe these mussels,
as the sj)eeitic name implies, are eaten in large (quantities, but with us they form a very
inconsiderable portion of the diet of people living near the shore. The cause of this
neglect may lie in the fact that they are said to be poisonous to some people. In some
regions they are gathered in immense quantities and used as manure. In France the
natural growth is far from sufficient to su])jdy the demand for table jjurposes, and
hence large tracts near the shore are used for their cultivation. Numerous sticks are
driven firmly into the bottom, and the ends which project above the surface of the
mud are interwoven with a wicker-work which affords an anchorage for large quantities
of mussels. At high tide these are covered, but at low water they are exposed, and it
is at this time that they are gathered for the market.

Although the mussels are anchored by a byssus, they are not compelled to live
sedentary lives, for at will they can drop the byssus and move about by the aid of
their slender foot. They can even climb, and their method of accom])lishing this is
interesting. The foot is moved about in tlie direction in which they wish to go, and
a byssal thread is attached. This supports the animal while the foot is again extended,
and another thread applied to a more distant point. By continued repetitions of this
operation the heavy shell is gradually lifted to the desired situation. Mi/tilus edulis
flourishes best in the zone between high and low water marks, and a little below,
although specimens are frequently dredged in much deeper water.

In Mytilus the umbones of the shell are terminal, and the hinge is either toothless
or furnished Avith minute teeth, while in Modiolus the umbones are a little behind the
end of the shell, a distinction which is well shown in our figures. Modiolus plicatulus

MOLLUSCS.

267

is a shore-inhabiting species, varying in color from nearly clear yellow to dark bronze
green, and ornamented with a series of radiating ridges. It likes especially shores
where a slight admixture of fresh
water renders the sea brackish.
Another S23ecies, Modiolus modi-
olus, is larger, and lives at ex-
treme low water mark, and be-
low. The surface of the shell
is not ribbed, but sj^ecimens
from sheltered localities have
the epidermis of the external
surface produced into bristles
and hairs. It occurs on our shores as well as those of Europe.

In Lithodomus the shell is small, long, and nearly cylindrical, resembling somewhat a
date ; and is covered with a thick, dark epidermis. In the young a byssus is spun, but
not by tlie adult, wliich excavates a hole in some soft rock, in which it subsecpiently lives.

Motliolns plicalulus.

Fiti. 279. — Lithndomui, Itthophat/aij in ith buiiuws.

Like all rock-excavating forms, it is not known how it bores its holes, a question which
will be mentioned again when treating of the family Pholadidre on a subsequent page.
Three species of Crenella (small thin shells with one tooth in each hinge, and straight
beaks) are found in our northern shores, one extending to the south of Cape Cod.

The species of Pinna have long, triangular shells, tapering to an acute angle at the
umbones. The shells are very thin and delicate, and are usually ornamented exteriorly
by large or small scale-like projections. The animals spin a very large and strong
byssus, which, as a curiosity, has been used in textile arts, the product someyvhat
resembling silk.

The last number of this family whieli needs mention is the form which science has
at last decided shall be called Drelssena pobjniorpha. Its specific name is indicative

268

L 0 WE 11 IN VER TEBliA TES.

tv-

Fig. 280. — Modiolus modiolus.

of its many vagaries of shapes, a fact which has led to its desci-iption under a large
number of generic and specific names. The shell is much like that of Mi/tilus, but in

the animal some important differ-
ences may be observed. The
mantle is closed, leaving only a
■small opening for the byssus,
while at the posterior end a short
siphon is formed. The most in-
teresting fact in connection with
Dreissena is its distribution. It
is a native of the Ar:d and Cas-
pian Seas, and was discovered by
Pallas in 1769 at the mouth of
the Volga. Later it was found
in the livers flowing into the Black Sea, and from these it is supposed to have been
transported into the rivers of Germany by the pontoon trains during the Napoleonic
wars. Its introduction into England in 1824 is supposed to have been effected by
means of foreign timber, and now it is a recognized member of the fauna of almost
all parts of Europe. In London it has proved itself something of a nuisance, as it has
obtained entrance to the ])ipes which suppl)^ the city with water.

The family Arcad.e embraces thick equivalve shells covered with a thick, often
haii'y, epidermis. The hinge ligament is external, and the hinge itself is very charac-
teristic, being formed of a large mimber of teeth arranged in a single row like those
of a comb. Both adductor muscles are present, and equally large, producing corre-
sponding imju-essions on the shell. The edges of the mantle are free, and the gills
terminate in free filaments. The foot is large, but very variously shaped.

Of the genus Area numerous subgenera ha\'e been made, and many species com-
nmnly parade un<ler the names Byssoarca, iSccqyharca, Art/iiia, Purallelipedum, etc.
For our jnirpose this refinement of classification is
not necessary, and we here acce])t tlie genus with
the Lamarekian signification. With this classifica-
tion we may define Area as a genus in which the
hinge teeth are nearly ecpial, and form a straight
line, the shell is ventricose, the umbones are widely
separated, and the free edges of the shell are fi'c-
quently gaping. Area noae, Noah's ark, received its

■T' r^f»— T ■ '^"TVtW>

Fig. 281. — Area note.

/:1?r%-.

I fran^rcrsa.

smaller, A. trans rer.srr.
as the 'bloody clam,'
the tissues are filled.

name from some queer fancy existing in the mind of Lin-

na'us. It secretes itself under stones at low water in the

Mediterranean, and closes the gape of its shell with a byssal

structure shaped like a cone, and composed of numerous

thin plates. Occasionally violet-colored pearls are found in

this species. On our eastern coast three s[)ecies occur ; a

\ ery thick and heavy form known as Area ponderosa, a

more closely ribbed species, A. ixxuta, and the longer and

Further south other species occur. Area pexata is known

on account of the red gills and the red fluid with which

It is covered with a thick, hairy epidermis, and has from

thirty-two to thirty-six radiating ribs on the outer surface of the shell. In Area

MOLLUSCS.

269

transversa the i-ibs are about the same in miniber, but the greater length of the
shell readily distinguishes it. Both these species occur under stones near low-water
mark. Area tortuosa of the Chinese seas is remarkable for the way in which tlie
valves are twisted. It is very common in collections. The species of Pectunculus
have a nearly circular outline, and the row of comb-like hinge teeth are arranged in a
circular arc. As the shell grows, the number of teeth increases by additions to either
end of the series.

The following genera are frequently sej)arated under a family, NirruuD.E, but for
our purposes they can be retained, as in the
older works, as members of the Arcadie.
Nitcula embraces small trigonal forms cov-
ered with an olive epidermis and a simjile
pallial line. The species are mostly inhalii-
tants of the colder waters of the northern
hemisphere. Leda is closely similar to Nu-
cula, but lias a small pallial sinus, and the

shell is much longer. Yoldia, like the other
genera, is boreal in its distribution ; in shape
and pallial sinus it is much like Leda, but the
siphons are long and slender. Of the several
species we need mention but two. Yoldia liin-
at'ula is a very long sjiecies, which, according
to Dr. Mighels, has the i^ower of leaping "to
an astonishing height, exceeding, in this faculty,
the scallop-shells." Yoldia thruccpformis is
larger and comparatively shorter. For a long
time it was among the rarest of our New England shells, and the only source of supply
was the examination of fish stomachs. More recently the various dredging expeditions
have found them in large numbers, and the writer remembers that on one occasion
the dredge brought up about two bushels of nothing but dead specimens of this
species.

Of the Teigonidjs, a small and nearly extinct family, Imt little need be said. The
two valves of the shell are equal, somewhat triangular in outline, pearly inside, and
are marked by a simple pallial line. The hinge ligament is external, and the few
hinge teeth are diverging. A somewhat unusual feature is found in the posteriorly
directed umbones. The margins of the mantle
are free, the foot is large and long, and the labial
palpi small and pointed. The few existing spe-
cies belong to the genus Tr'if/o)iia., and are found
only in the Australian seas. They are very
active and are supposed to wander about on
the sea bottom.

Fai- more prominent is the next family, which
embraces the fi-esh-water mussels, the Unionid^
or Naiad.e of science. Nearly fifteen hundred
nominal species exist in the fresh waters of the world, a large proportion being found
in the streams and ponds of the United States. It seems probable that further investi-
gations will relegate a large number of these so-called species into synonymy, as many

Fig. ;^S4. — Yoldia thracc^/ormis.

Fig. 2S5.

-llin'n rompfnnatus, with foot and
siphons extended.

270

L 0 WER IN VER TEBRA TES.

Fig. l'SG. — Glocliidiuin
Unio, still witliiii tlu'
nieiiibrane; b, byssus; ni

seem to be founded on individual variation. The shells are usually long, equivalve,
and are covered e.xternally with a smooth, thick epidermis, which is of various shades
of brown, olive, and green. Internally the shell is pearly; sometimes white, at others
dark pink or almost purple. The hinge ligament is large and external, and the ante-
rior hinge teeth are large and thick, the posterior compressed and laminar ; or all may
be wanting. Both adductor muscles are present. The mantle edges are united
posteriorly so as to form a rudimentary siphon. The foot is very large and tongue-
shaped, and in the adult occasionally secretes a byssus.

One of the most interesting features connected with the fresh-water mussels is found
in their development. The eggs are carried in brood pouches
between the lamelliB of the outer gills, and there undergo their
early development, the details of which need not be described
Iiere. Eventually a slicll is formed, which soon divides into two
valves united by a straight hinge. Soon at the fore extremities
of each valve a strong beak-like process is developed, and a little
later a byssus is secreted. Next, peculiar sense organs are
formed on the inner surface of the mantle, the function of
j,j which is, doubtless, to ascertain the presence of fishes. Now
the young is in the coiulition known as a Glochidiuni, and when
.idductor muscle; s, sense {jje mother is under natural conditions or tilaeed in a tank -witli

org-ans; f, teeth; r, velum. ^

fish, the young are expelled from the brood jioui'h and almost
innnediatcly attach themselves to some submerged object by means of the byssus. If
no fishes be present, the mother will retain the young for a long time after the glochi-
diura stage has been reached. As soon as an opportunity is afforded, the glochidia
attach themselves to the gills, fins, or other jiarts of a fish, by closing the valves of the
shell and holding on by the si)iny beaks mentioned above. Here they undergo an
extensive metamorphosis, in which the single adductor muscle disappears and is
replaced by the two of the adult, the gills appear, the sense organs atrophy, and,
according to one author, the shell and even the mantle lobes are formed anew.
Finally, when all the organs except those concerned in reproduction are formed, the
embryo quits its host and sinks to the bottom, where by a regular growth it attains
the adnlt condition. This parasitic or semi-jiarasitie life is very unusual among the
Mollusca.

The Unionidae live in still water or in running streams, usually about half buric<l
in the mud. They do not, however, lead sedentary lives, but bur-
row or plough along the bottom, the part of the shell which con-
tains the siphons being above the surface of the gravel or mud.
According to Dr. Lea one species occurring in the United States
{Margaritana dehiscens) buries itself completely in the mud and
draws its water and food through a tube, as do so many of the
siphonated marine forms.

In the typical genus Unio, the hinge is provided with one or
two anterior and one posterioi- teeth in one valve, and two anterior
and two posterior in the other. The shell is smooth or ribbed or
even spined, and the variations in shape are extraordinary. In
some of the species the valves become soldered together at tlie
hinge, so that motion would be impossible were it not for the fact that a fracture takes
jilace near the line of junction, so that one v.alve bears two wings while the other has

"^

'^

Fig. 287.— f '«io spinosuft.

MOLLUSCS.

271

Fig. 2S8. — (7h io clams.

none. This f.ict has been used by Dr. Lea to divide the numerous species of f '/^'o
into two groups, those with soldered hinge being called syuiphynote, and those with
the normal structure asymphynote forms. Althougli we have a vast number of species
of Uiiio, there is but little of popular interest to be said concerning them.

ITargaritana (or Alasmodon) is closely similar to Unio, the only differences being
in tlie details of the hinge teeth. M. margaritifera, whicli occurs both in Europe
and in the northern United States, is espe-
cially noticeable from the fact that it pro-
duces pearls which are frequently valuable,
equalling those of the true pearl oyster de-
scribed on a preceding page. During the
Roman occupation of the British Isles, these
■pearls were famous, and in more modern times
the search has been eontiinied, especially in
Scotland, Bavaria, and Bohemia. These pearls
not unfrequently have a slight pinkish hue,
which is permanent. In the United States the
search for these has never been prosecuted
with any great vigor, although the writer has seen several tine pearls found in New
York State. This branch of the pearl fishery can be conducted with more ease and less
danger tlian that of the true pearl oyster, since the species can be found in brooks and
rivers which can be waded, and which are so clear as to render the collection of the
mussels an easy task. All the pearls collected have a value, no matter how impeifect,
since pearls can be propei-ly polished only by the use of pearl powder, and for this pur-
pose inferior pearls are as good as those of the best quality.

The only other genus which needs mention is Anodonta, in which as the name
indicates, the hinge teeth are lacking. The species have a light, tliin, smooth shell,
and, like the preceding forms, are found both in streams and ponds. Regarding tlie

names to be applied to our North Ameri-
can Unionidse, the utmost confusion exists.
Many forms were described almost simul-
taneously by Rafinesque, Say, Hildreth,
Barnes, Lea, and Conrad. The descriptions
uf the latter author, like all his work, wei'e
decidedly poor, and it is said that here, as
elsewhere, he described, from accounts fur-
nished him by peojile other than natural-
ists, shells which he had never seen. To
make confusion worse confounded, Rafines-
que, in his later years, when his intellect was
clouded, named a set of shells wliich now
figure as his 'types.' Besides this, almost
innumerable questions of priority exist ; the
sUghtest variation of outline has been seized upon to form new species, and in many
ways the whole subject has been tortured and twisted so that the jierson who in the
future endeavors to unravel the skein will have a task of no small difficulty.

In the preceding families of Acephals we have found considerable variation in the
free or united edges of the mantle, and in the presence or absence of siphonal tubes.

Fig. '2»V. — Unio fiexttosus.

272 LOWER INVERTEBRATES.

Ill all the remaining families the siphons are well developed, elongate and tubular,
and the edges of the mantle are united to a greater or less extent. In the Chanudie,
Tridacnida;, Hippuritida-, Cardiida', Lucinidie, Cyeladida', and Cyprinid:e, the i)allial
line produced by the edge of the mantle on the shell is simple, while in all the remain-
ing families at the posterior end of the shell it makes a re-entrant angle known as the
pallial sinus. This is produced by the great development of the sijihonal muscles.

The members of the ChamidvE are thick, irregular, inequivalve shells, with exter-
nal hinsje ligament and strongly developed hinge teeth, one in one valve and two in
the other. The mantle margins are united, leaving only the small siphons and a
small opening for the foot. The living species are found in the tropical seas of both
hemispheres, and all, both recent and fossil, are usually attached to some rock or shell
by one of the umbones. In C/iama the shell is lamellar in texture and the nmbones
are coiled in a spiral ; but this peculiarity reaches its greatest development in the fossil
genus Diceras, either valve of which, seen alone, would be taken for the shell of a
gasteropod until a closer examination showed the hinge, muscular impressions, etc.

The HiPPURiTiD-E (ranked as an order, Rudistes, by Lamarck) is usually placed here,
but its position is far from certain. The family is characteristic of the rocks of the
cretaceous age and in some parts of Europe have given to certain beds the name of
Hipj)urite limestone. They are also found on our continent. Tiie shells are sui generis;
the two valves are very unequal, one being frequently ver}' flat, while the other is
immensely drawn out, in one form resembling a cow's horn, and giving rise to the
name Hij>purite& cornu-vaccarutn. The shells were attached, and frequently the
larger valve was chambered so that in forms like Caprindki it bore no inconsiderable
resemblance to the chambered shells of the cephalopods. The position which these
forms should occupy in the animal kingdom has been very diffei-ently regarded by
different authors. Besides being placed in varying relationships among tlie Acephals,
they have been considered as corals, barnacles, worms, and various combinations of
these distinct groups. The ])rincipal features which place them among the bivalve
molluscs are the structure of the shells, which are hinged together ami furnished with
an internal cartilage, the presence of two adductor muscles and a well-marked jiallial
line. One noticeable peculiarity is found in Ifippuritcs, where the free valve "is per-
forated by radiating canals which open around its inner margin, and communicate with,
the n])per surface by numerous pores, as if to supply the interior with filtei-ed water."
In other genera there is no trace of these canals.

The Tkidacnid.e, which are all inhabitants of the eastern seas, contain the largest
bivalves known. The shell is regular and equivalve, the valves being ornamented by
strong^ ribs radiating from the umljones. The shell is very hard, almost every trace of
organic matter being removed. The hinge ligament is external, and there are either
one or two cardinal teeth in each valve, and one posterior tooth in one, and two in the
other. The foot is comparatively small, fingei--like, and ]:>rovided with a byssal groove.
Some of the species spin a byssus, but otliers do not. The adductor muscle is single,
and there are two gills on either side, the outer ones composed of but a single
lamina.

The genus Tridacnu embraces some very large forms, and the generic name is
given in allusion to this fact. The ancients used to tell of an Indian oyster which was
so large that it required three bites {tri and dakno) to devour one of them, and so,
when a more modern science came to name these forms, the old terms Avas resurrected
and applied as a generic name. The appropriateness of it will readily be seen when it

MOLLUSCS.

273

Fig. 290. — Tridacua mut'tca.

is stated tliat the soft parts of Tridacna giy<is will sometimes weigh twenty pounds.
The shells of this same species will sometimes, together, weigh five huudrod pounds,
and in some of the churches of France they are
employed to hold the holy-water, a use which
well accords with the beautiful white of the in-
ner surface of the shell. This species and the
smaller T. squamosa are very common in col-
lections, the first having the ribs of the valves
nearly smooth, the other having them orna-
mented by large foliaceous processes. Both
these species are of considerable importance to
the South Sea Islanders, as they afford an im-
portant part of the food sujjply. The giant clam
is also useful from a mechanical point of view.
In many of these islands, stones are unknown,
but, as a substitute, the natives make their knives
and axes from the fragments of this shell. In
one species the gills are bright blue.

Ilippopi/s, which differs but slightly from
Tridacna, has a similar distribution, and the
common species, H. macnkUus, is found in almost every collection. The ribs on
the outside are much smaller and more numerous than in the other genus, and scat-
tered over the outside are mimerous little, scale-like jirojections. The color, both
inside and out, is a delicate, creamy white, ornamented on the exterior with small
blotches of lake. The generic name means horse-foot, but the common name is the
bear's-paw clam. The applicability of either is not very evident.

The name Cabdiid^ is applied to the next family which we have to consider on
account of the heart-shaped outline which the species jiresent when viewed from the end.
The valves are equal and swollen out, and the tunbones are rolled inward, so that the
appearance is like the con\entional heart, which, it may be remarked, resembles no
heart existing in nature. The hinge ligament is external, and the hinge teeth are two
in each valve beneath the umbones, and one in each on either side of the central ones.
The external surface of the shell is usually radiately ribbed, the ornamentation on the
posterior part differing from that in front. The edges of the mantle are united, so
that a small slit is left for the protrusion of the strong, sickle-shaped foot, wdiich plays
a very important part in the locomotion of these molluscs. The siphons are usually
very small, but occasionally they are better developed, and at stu'h times there is a
slight indication of a sinus in the pallia! line.

CanUitm, with its various subdivisions, embracing about a hundred and fifty species,
is found in all the seas of the world, living in shallow water, from low tide down to a
hundred and fifty fathoms. The shell is strongly ribbed and very swollen. Our
largest species is Cardiinn islandicum which is found north of Cape Cod. Other
smaller species are found on our coasts, one of which ( C. puinulutum) occurs as far
south as Long Island Sound. These shells are known as cockles, and one species is
eaten in England. They prefer sandy bays near low water, and are usually found
in large immliers together.

In Lmvicardium, as the name indicates, the surface is nearly smooth, and our
single species ranges from the West Indies to Nova Scotia, being common in the w'aters

VOL. I. — IS

274

L 0 WER IN VER TEBR A TES.

south of Cape Cod. Serri2jes is noticeable from the fact that the cardinal hinge teeth
have disa]ipearod ; the species S. f/ronlandica occurs in the i)olar seas, extending south
on our coasts to Massachusetts Bay. Ilernicurdiuni, is a tro[)ical genus, in which the
posterior jjart of the sliell is separated from the anterior by an alirupl angle. The
cardinal teeth are distinct.

Fig. IVl. — Lucma den-
tata.

tiuii, cockle, Willi the foot extended.

The LuciNTD.E embrace forms with a circular outline, one or two cardinal hinge
teeth, and the laterals one or obsolete. The hinge ligament is external or jiartially
intei-nal. The mantle is (ijieii in front, but l)eliind is united into one or two short
siphonal tubes. Tlie foot is long, cylindrical, or woi-m-sha])ed. J^uchia is reju-esented
on our coast by two .sjiecies, one of wliich, L. dmiatd (soTnetimes included in a sub-
genus Cijclus) is noticeable fcir the jieculiar ornnnieiit:iti()ii of tlie
valves. The shell is pure white, and exhibits tiie regular lines of
growth, but over these is laid a second series of lines in a manner
difficult to descrilie in a few words, Viut readily understood from
the figure. One or t«'o other genera {Strif/iUa, Choristodon) be-
longing to the Telliiadaj are ornamented in a similar manner.

In JLticina fiIos(f, which is not \ery cuninKni, tliese striations
ai'e absent, and the shell is roughened by a nunibcr of concentric
lamellar ridges with smaller, thread-like ridges between.

In Cri/ptodcn. the hinge teeth are wanting. Ungulinu, a genus of the eastern seas,
is noticeable from the fact that it excavates winding galleries in the coral on the reefs
where it is found. Kcllia 2->lanidata is foiuid on the northern coast of America, under
stones, at low-water mai-k, and other species in vai'ious ])arts of the world live above
the reach of ordinary tides, or burrow in sandstone. Tliey creep about freely, and
anchor themselves by a liyssus at jileasure. One species of Montacuta occurring in
Great Britain (il/i sidiMriatd) is to be mentioned because it has never been found
except attached to the spines of the sea-urcliin, Spatauf/vs pinj>ii)-e)/s. It cannot be
regarded as a true parasite, for not only has it no organs by wliich to feed ujkui the
urchin, bnt it is never attached to any of the soft jiarts of its host. It is ratlicr to be
regarded as a mess-mate or commensal, obtaining its food from the same source as
does the ui-chin.

In the fresli waters the world over occurs a group of usually small bivalve shells.

MOLLUSCS.

275

covered with an amber or brown epidermis, while in tlie brackish waters of warmer
countries occur some larg-er forms. The family under which these are assembled is
variously known as Cycladid^ or Cyeenid^e, the latter name being preferable. In
all, the shell is nearly circular in outline, the ligament is external, the hinge is provided
with several teeth. Usually there are apparent indications of u pallial sinus, most
marked in the American species.

C'y;'e/<« is the typical genus and embraces over a hundred nominal species, which
live in brackish water in the warmer parts of the globe. They are frequently found
buried in the mud of mangrove swamps, where the tide rises and falls slightly, but
where the admixture of rain renders the water less dense than that of the ocean.
Cyrena carolinensis occurs in the rivers and swamps of some of our southern states.
lu ourBortheru states the family is rei)resented by the genera /Sphcerutm and Pm-
diu?n, our fauna containing about fifty S])ecies of both genera. Sphcerhim (known in
some of the older works as Ci/das) has the shell nearly equilateral, tlie hinge teeth
minute and rather weak, and two nearly separate siphons. In Flsidiimi the part of
tlie shell in front of the umbones is larger than that behind, the teeth are stronger,
and the two siphons are tniited tlie whole length. Tlio sp<>cies abound in the still
water of some of our ponds,
and are very active.

The CvpRiNioji: is a much
larger family than the last,
and its members are inhabi-
tants of salt water. The
shell is regular, oval, and
equivalve, and is covered
with a thick, strong epider-
mis. The hinge ligament is
usually external, and the
hinge is provided with from
one to three cardinal teeth,
and usually one posterior
lateral in each valve. The
margins of the mantle are
fringed, the pallial line sim-
ple, and the two siphonal
tubes are short.

Cyprina islandica is a
large boreal shell, common in sandy bottoms north of Cape Cod, but is less frequently
met with south of that barrier. The hinge has three
unequal diverging cardinal teeth and one lateriil.
The shell is thick and heavy, and the color in the
young is very light brown, but old specimens are
very dark. With age, the c]iidermis, near the um-
F'G- 294^— ^.^s""'fe bones, usually disai)pears, and the shell itself is fre-
quently eroded. Large specimens measure four
inches across. Several sjiecies of Astarte are found on our northern
coasts, all of which can be recognized by the smooth or concentrically furrowed surface,
and the two hinge teeth in each valve. The shell is covered with a strong epidermis.

Fig. 295. — Ci/rlo-
cardia novan'glwe.

270

LOWER INVERTEBRATES.

In Cyclocardia the shell is radiately ribbed, and nearly circular in outline. Cardinal,
but no lateral teeth are present. Isocardia is a genus with very ventricose shell, and
with the beaks regularly inrolled. Isocardia cor is found in the Mediterranean.

With the VENERiDiE we enter upon a grouj) embracing all the remaining bivalves,
in which the siphons are well developed and the pallial sinus well marked. In the
Veneridae the shell varies in outline between nearly spherical to oblong, the ligament
is external, and usually there are three diverging teeth in each valve. The siphonal
tubes are unequally developed, and are united at the base. The foot is tongue-shaped,
and compressed, and the triangular labial palpi are very large. The forms embraced
in this family include some of the handsomest of the Ijivalve molluscs, the distribution
of color being fretpiently very striking, chevron-shaped lines being most frequent.

In Venus, the typical genus, the shell is oval and thick, and the pallial sinus is
small and angular. Most important to us is the quahog, round clam, or hard-shell
clam ( Venus merceymria), which forms a considerable article of diet in those regions
where the long clam, or soft-shell clam {Mija arenaria), is not to be had. In its
range it extends from Texas to Cape Cod, but north of that cape it is comparatively
rare and local. It is " common on sandy shores, living chiefly on the sandy and muddy
flats, just beyond low-water mark, but is often found on the portion laid bare at low-
water of spring tides. It also inhabits the estuaries, where it most abounds. It bur-
rows a short distance below the surface, but is frequently found crawling at the surface,

with the shell partly
exposed." The mantle
is widely open in front,
allowing the large foot
to be jilaced in almost
any position. The si-
]>honal tubes are united
for quite a distance.
"This species is taken
in large quantities for
food, and may almost
always be seen of vari-
ous sizes in our markets.
The small or moderate-
sized ones are generally
preferred to the full-
grown clams. Most of
those sold come from the muddy estuaries, in shallow water, and are fished up chiefly
by means of long rakes and tongs, such as are often used for obtaining oysters. Some-
times they are dredged, and occasionally they can be obtained by hand at or just below
low-water mark. These estuary specimens usually have rough, thick, dull-white or
mud-stained shells, but those from the sandy shores outside have thinner and more
delicate shells, often with high, thin ribs, especially when young ; and, in some varieties,
the shell is hand,somely marked with angular or zigzag lines or streaks of red oi
brown."

In most of the shells, when nearly full-grown, the borders of the interior of the
valves is colored purple to the distance of about half an inch from the margin, and it
was by breaking up this portion and converting it into beads that the Indians of New

Fig. 29G. — Vemis mercenaria, quahog, with foot, siphons, and edge of mantle
extended.

s »

<i

to

^

fi

<

a.

H

§

S^

g

o

S^

tri

c:;

t-i

^

n

>S*

cc

o

S

CD

i-

MOLLUSCS. 277

England made tlieir puriilo wanij)uni, or gi/vka/i./iock, wliieli was regarded as twice as
valuable as the white money, or womponi proper. This latter was made from various
shells, but mostl}' from Busycoii.

Many other species of Venus, in its broader sense, are found in the warmer seas of
the world, the west coast of America being better supplied than the east.

Cytherea and its sub-genus UalUsta are readily distinguished from Venus by the
presence of an anterior lateral tooth in the left valve, which tits into a corresponding
depression in the other. Like the last genus it is rich in species, especially in the
warmer seas of the world. Our northern C. convexa has an outline much like that of
the quahog, but its dead white surface does not render it as attractive as its southern
relative, CaUista giyanteu, which is found on our southern coasts. Cytherea lusoria
is a Chinese species, which derives its specific name from the fact that the inhabitants
of the celestial empire paint certain figures on the inner surface of the valves, and
then employ them in some of their many games of chance. Cytherea scnpta has a
ground of white or yellow, over which is laid a series of zig-zag reddish-brown lines,
which require a rather vivid imagination to be regarded as resembling writing. It
comes from the Indian Ocean, as does the C erycimi. C. dione, from the west coast
of America, is a remarkalde s]iecies, from the fact that it is ornamented by a series of
long slender sitines, running in a row down the pos-
terior side of the shell, from the umbones to the mar-
gin. The color is a rosy purple, varying considerably
in depth. In the more recent systems of classification
it is made the type of the genus Dione.

Meroe embraces a few species of oval shells, with
three cardinal teeth and a long anterior tooth. The
general shape can be seen from our figure, but there is

nothing of popular interest to be said concerning the Fir,. 297. — .Unni'.

species. Dosinia is represented on our shores by a

species (2). discus), the specific name of which is very apt. The shell is Hat, and
nearly circular in outline; the siphons are imited, and the foot is large.

Gemma embraces only a single species, found on our coast, and known under the
repetitive name of Gemma yenima. In size it is minute, scarcely more than an eighth
of an inch in length, and in color it is a yellowish white, or rosy, tipped posteriorly
with an amethystine purple, so that the name is very a])propriate. It wottld ajipear
that it was known to the early settlers of this country, and that they sent specimens
of it, along with other curiosities, to the old world ; and yet it was unknown to natu-
ralists until the year 18.34, when the eminent engineer. General Totten, who was a
good naturalist with.al, published a desci-ij)tion of it. It is an active species, found on
sandy shores, where it burrows quickly. One of the most interesting facts known in
connection with it is that it retains the young inside its valves until the shells are fully
formed, sometimes tliirty young being found inside of the parent shell.

No species of the genus Tapes occur on our coasts, but the seas of other parts of
the globe contain nearly a hundred species. The shells are long, the siphons separate
at their extremities, and the long, slender foot spins a byssus. Many of the species
are ornamented with zig-zag lines, of darker color, and in Europe, especially on the
Mediterranean coast, T. yeographica is used as an article of food.

The family Petricolid^ is a small one, and its only member which requires men-
tion is the form known as Petricola pholadiformis. This is a thin, long shell, orna-

278

LOWER INVERTEBRATES.

Fig. liyb. — I'ttricola pkuUidij'onnis.

merited with radiating ribs, arranged much like those in J'holas, whence the specific
name. The sliell caimot be coiu])letely closed, but gapes, while the mantle is almost

entirely united in front, leaving but a slight open-
ing for the small, pointed foot. It has a rather
extensive distribution, reaching from Nova Scotia
to Texas ; and Professor Verrill writes that he has
received specimens from the Gulf of California which
are scarcely to be distinguished from this. It is
sometimes found among rocks and stones, below
low-water mark, but more frequently it makes deep burrows in stiff mud or clay
bottoms, climbing up and down in them by means of its slender and flexible foot.
The siphons are very long, and are united for only a short distance. Other species of
Petricola excavate and occupy burrows in the softer limestone rocks, and from this fact
the generic name has been given. I am not aware that this habit has been noticed in
our species. The shell of P. pholadiformis reaches a length of two and a half inches,
but specimens over two inches long are uncommon. In color it is a chalky white.

The MACTEiDiE embraces a considerable number of trigonal equivalve shells, which
can be completely closed, or which gape slightly. The ligament is usually internal, and
contained in a deep pit, but occasionally it is external ; the hinge has two diverging
cardinal teeth, and laterals are
frequently present. The out-
side of the shell is covered with
a thick epidermis. The pallial
sinus is short, and rounded or
angular, and the siphonal tubes
are united and have their ex-
tremities fringed with small
tentacles.

Mactra solidissima and the
closely allied 31. ovalis are
known along our northern
coasts as hen-clam, sea-clam,
and surf-clam, these names
properly belonging to the more
connnon and more littoral spe-
cies first mentioned. The first is distributed from the Carolinas to Labrador, wliile
the second is only found north of Cape Cod. On every sandy beach Jf. solidissima
occurs in large numbers, and after gales the other species is thrown uji on the shore.
They are used in a limited way for food, and when properly prejiared they make a
chowder no less jialatable than the 3I//a are?iaria, so extensively used. The toughness
of the older individuals prevents their more extensive use, and their jn-eparation calls
for the use of the cho])]>ino;-knife. The species are very active, and, instead of leading
sedentary lives in liurrows, they ploiigh through the sand by means of their well-de-
veloped foot. They have a considerable leaping ability, and many a time have I
known a basket full at night, and left in a 'trap,' to be half emptied in the moi'uing,
the clams leaping out by means of their foot. The species of Jlactra are valuable for
the student of molluscan anatomy, from the fact that their ganglia and nerves are col-
ored a reddish hue, and are thus more easily distinguished, and dissected out. than in

Fig. iya. — Maclr

MOLLUSCS.

279

Fig. 300. — MtU'mla lateralis.

Fig. 301. — liaugia cyrenokles.

iiiany otlicr forms. Jfactra solidigsima occasionally reaches a length of over six inches,
lias the carilinal teeth delicate, and h.as a shallow pallial sinus. JI. ooalls but rarely
exceeds four inches in length, and has the teeth short and
the sinus deep. Separated from Jfactra proper by an angu-
lar pallial sinus is the sub-genus Muliniu, of which one spe-
cies, 2[aHnia lateralis, occurs nearly the whole length of our
eastern coast.

lian.gia (also known as Gnathodon) is a brackish-water
genus, represented in the southern United States by the spe-
cies R. cyrenoides. In the gulf states this species occurs in vast numbers. Banks of

dead shells, three or four feet in thick-
ness, occur ill many places, some of
them twenty miles inland. The city
of Mobile is built on one of these
banks, while the road over which the
inliabitants of New Orleans travel in
order to reach Lake Pontchartrain " is
made of these shells, procured from
the east end of the lake, where there
is a mound of them a mile long, fifteen
feet high, and from twenty to sixty
yards wide ; in some places it is twenty
feet above the level of the lake."
The f.-imily Tellenid.e vies with the Venerid;e in its beautifully-colored s|]ecies.
Like the members of that family, they are mostly inhal)itaiits of tlie warmer seas of the
world, the small number of species which stray into the more northern waters
being dull colored, and far less attractive than their tropical relatives. The shells are
long, compressed, and usually closed and e(jui-valve ; and one marked feature that is
generally found is that the half of the shell in front of the umbones is longer tliaii that
behind them. The cardinal teeth are at most two in number; the lateral teeth are oc-
casionally obsolete. The hinge lig.ament is usually external and posterior. The mantle
is widely open in front, and the two very long and slender siphonal tubes are com-
pletely separated. The foot is triangular and corai)resse(l. In most species the shell
is very dense, and highly polished, and not infrequently is white, enlivened by bands
or strij)es of delicate shades of red or yellow, while in others the effect is heightened
by the finely sculptured lines.

In TaUiiia, which reaches its highest development in the Indian Ocean, the shell is
rounded in front and angular posteriorly, a fold running from the angle to the umbo.
The siphons are very long, and can be extended to at least twice the length of the
shell, and, as a necessary sequence of such extensibility, tlie pallial sinus is very wide
and deep. In Strigilla the sui'face is ornamented with
divaricating lines, like those of Cijclas, described on a ]ire-
ceding page.

Our northern forms belonging to this family are dull
colored and unattractive. Tellina tenera, which occurs f r( nn
Florida to the Gulf of St. L.awrence, is an exception, for tlie
delicate rose-color which tinges the otherwise white shell makes it an object of
beauty. The siphons are very long, several times the length of the body, and hence

Fig. 302. — Tellina tenera.

280

LOWER INVERTEBRATES.

Fig. 30J. - 1/

Fig. 304. — Macoma
J'usca.

tliis Species can burrow beneath the sand, and thence e.vtend its long siphons to the
surface. In Macoma the thin wliite sliell is covered with a dusky epidermis. M.
sabulosa is a more northern form, extend-
ing as far south as Long Island Sound, wliik'
tlie more common 31. fusca reaches the
coast of Georgia. In muddy places tliis
latter species possesses but little beauty.
liut when living in clean sand the e))idermis
becomes thinner, and the shells frequently
liave a delicate rose or lemon color.
Donax is an easily recognizable genus, in wliieh tlie posterior end of the shell
appears as if cut off at a more or less oblique angle. The sjiecies occur in tropical
and semi-tropical regions, where they bury an inch or two beneath the sandy shores.
Our two species, J), fossor and D. variabilis, occur abundantly in some places in the
southern states, the former reaching as far north as New Jersey and Long Island.

Space will allow but a mere mention of the other prominent genera of this family ;
Paphia, Semele, JScrohicalariu, Fsaminohia, Saiujidnolaria, etc., which embrace many
beautiful forms, but only few of which anything of pojiular interest can be said.
Scrobicidaria piperata of the Mediterranean is occasionally eaten, and receives its
specific name from its ])eppery taste.

The MyiDjE has an ini]>ortance among the molluscs of the northern seas far out of
proportion to the number of species, for the long clam, or soft-shell clam, is its most
prominent member. In all the family the shell is thick and strong, and when closed
as far as possible, it still gapes at one or l)oth ends. Tlic hinge cartilage is internal,
and rests in a peculiar ])rocess of the left valve, as diagrammatically shown in Fig.
265, on a preceding page. The foot is small, the mantle margins have but a slight
pedal gape, while the very extensible siphons are united their whole extent.

M>/a urenuria, the clam par excellence, which figures so largely in the celebrated
New England clam-bake, is found in all the northern seas of the world, and is too
well known to need any technical description. All along the coasts of the Eastern
States, every sandy shore, every mud flat, is full of them, and from every village and
hamlet the clam-digger goes forth at low tide to dig these esculent bivalves. The
clams live in deep burrows in the firm mud or sand, the shells sometimes being a foot
or fifteen inches beneath the surface. When the Hats are covered with water, his
clamshi]) extends his long siphons up through the burrow to the surface of th<> sand,
and through one of these tubes the water and its myriads of animalcules, is drawn
down into the shell, furnishing the gills with oxygen and the mouth with food,
and then the water, charged with carljonic acid and fcecal refuse, is forced out of the
other siphon. When the tide ebbs, the siphons are closed and partly withdrawn. Tlie
clam beiiins its burrow at a very early stage, and keeps enlarging and dee])ening it as
it grows older. An old clam dug up and left on the surface has hard work to make a
new burrow.

The white settlers were not the first to find out the ]ialatable (jualities of the clam,
the Indians knew it and loved it long ages before. On the shores of every promon-
tory and bay along the New England coast are old sliell heaps, 'kjokkenmc'iddings'
the archaeologist calls them, which tell of many a feast l)y the red man. The careful
explorer, by raking them over, finds not oidy the shells of the connnon dam, but those
of many other molluscs, and bones of various animals as well, together with the tools

MOLLUSCS.

281

and implements of the former inliabitnnts. In these heaps on the coast of Maine, tlie
bones of the now extinct great aulc have been found.

However eaten, whether raw, or in a cliowder, or fried, the clam is good, but best
of all is the clain-bake, where a long-continued fire heats the rocks red hot. Then the
cinders and ashes are swept away, a thin layer of rock-weed is laid on the hot stones,
the clams placed in the centre and covered with more of the rock-weed. The steam
generated cooks the clams in the most perfect manner.

A second species of Mija., M. triincata, occurs on our coast, and but one other is
known in the world. 3L/a tn(/ica(a, instead of being rounded at both extremities, is
truncated behind, while in the living specimen the epidermis is extended in the shape
of a tube, some six or seven inches in length, from the posterior edges of the shell.
This species lives below low-water mark, and is not coiiuuon south of Eastport. On
the English shores it is more common than Mi/a arenaria.

The species of Saxi.cava bore into hard mud, stones, etc., and have very irregular
and greatly distoi-ted shells, so that specific limits are far from certain. Probably our
only species is that figured, Saxicaoa arctica, but several others
have been described upon the variations of this form. Indeed,
Woodward states that no less than five genera and fifteen species
have been made upon the form known as S. riigosa, and since this
and iS. arctica are probably the same, the synonj'my of this protean
species is something awful to contemplate. In places where Ume-
stone is abundant, Saxicava bores holes in it to the depth of about six inches, and as
it is not at all careful where it goes, it
not infrequently cuts across the burrow , ^^f
of another individual. When a specimen ,.''
dies the soft parts decay, but the valves /
remain in the burrow, and another indi- /
vidual occupies the same burrow, seating '
itself " between the valves of its prede-
cessor. In this way four or five pairs of
shells may be frequently seen nested one
within the other."

Panopma is a genus of large shells,
the animal of which closely resembles
Saxicava. Panopcea norvefiica is a boreal species, specimens of which are occasionally

found in the stomachs of
fishes; the shell is covered
with a thick epidermis.

Glycimeris siliqua is the
otdy species of the genus
vuown, and presents several
noticeable peculiarities. It
is covered with a thick,
glossy - black epidermis,
while the interior of tlie
thick valves is rendered
very irregular by the great deposition of calcareous matter seemingly without rhyme
or reason. The animal is much larger than the shell, and the soft parts cannot be

Fig. 307. — Glycimeris siliqua.

282

L 0 WER IN VEll TEDRA TES.

drawn entirely within the valves. Like the last, it is boreal in its distribution, but it
is not uncommon in Massachusetts Bay.

The Anatinid.e is an almost extinct family. To-day it is represented by a few
species, but in geological time they played a much more important jjart than now,
their remains being found in the oldest paleozoic rocks. The internal surface of tho
shell is ])early, the external granular, and the hinge is usually toothless. About half a
dozen species are found on our coasts, representing tljc genera Pandora, Thnivia,
Per'qAonia and Lijoii&ia.

The SoLENiD.E, the family of the razor-clams, is next in order, and the tyjiical
forms, like Solen, well deserve the common name which has been given them. In all
the family the shell is long, and in some of the genera immensely so; at each end it
gapes, and the hinge teeth are usually two in one valve and tliree in the other. The
foot is very large, and more or less cylindrical, the siphons are short or moderate.
The old genus iSoleu lias recently been broken up, tliose with straight shells and one
tooth in each valve being retained in that genus, while those with the typical mind>er
of teeth, and usually slightly curved shells, belong to Ensis.

In American waters £Jnsis a.mericana is the razor-lish, or razor-clam. The shell
is long and sub-cylindrical, and bears no slight resemblance to the familiar tonsorial in-
strument. It is a common inhabitant of the sandy shores. These clams excavate large
elliptical holes, which penetrate downward, usually in a nearly vertical direction, to a
depth of two or three feet. Up and down this hole they go. When the tide is in, and
no danger is near, one end of the shell usually projects above the surrounding surface
of the sand for an inch or so, but a sudden jar startles them, and down they go with

great rajsidity. It is useless to at-
tempt to dig them out, for they
can burrow as fast as a man can
shovel out the sand, and besides
they have two or thi-ee feet the
start. 'Jlic jirocess of burrowing
is interesting. The foot is bevelled off to a point, and this is readily jiushed down
into the sand. Then the animal inflates the foot with water so that it becomes
bulbous at the extremity; this at the same time crowds aside the s;md and gives
the animal a hold whereby it can draw itself down. By a repetition of the process
it still further increases its distance from the surface. The razor-clam can start this
burrow wlien lying on the surface ; at first its progress is slow, but as soon as it gets
the shell in a vertical position, it goes much more rapidly.

The razor-clams are used for food, but to a far less extent than many other bivalves.
For this there are several reasons. First, it is not so common as the quahog or the
soft-shell clam, and, again, it is not so easily procured. We have already alluded to
the rajiidity with which it disappears when alarmed, and the recent in\estigations of
Dr. Sharp show that it does not depend, for its warning, upon the senses of sight and
feeling alone for its warnings of impending danger. On the ends of the siphons Dr.
Sharp finds organs of vision, very rudimentary, it is true, but still sufficient to recog-
nize various degrees of light and shade. His attention was called to this subject by
the fact that a shadow cast upon razor-clams exposed for sale caused them to innne-
diately withdraw their siphons. Histological investigation followed, which showed
that the essential jiarts of o]itic organs were present.

The fishermen, in procuring them, walk quickly uj) to the animal, and grasp it

Fio. ods. — 7?Hs/s amcricava, razor-clam.

MOLLUSCS.

283

Fig. 309. — Siliqua costata.

before it has time to retreat. In Europe tlie clam-digger pours a little salt down the
hole ; this brings the elam to the surface, when it is quickly grasped. If not success-
ful, no subsequent salting will arouse the clam. Where the water is still, another
method is adojjted. At low tide the fisherman goes over the flats and puts a little oil
near each hole. When the tide rises and the clams come to the surface, this oil marks
the spots where they are, and thus the fisherman is readily guided to them. These
clams are said to be very 'good, but as to their merits comjiarcd with JIaciru, J/i/a
Venus, and Ostrea, the writer can from his own ex-
perience say nothing.

Siliqua costata is another common species on our
northeastern coasts. The shells are covered with a
greenish epidermis, which is enlivened by one or two
rays of more or less vivid violet. On the inside of the
shell is ;i thickened rib running outward from the umbo.

This is one of the most common shells thrown up on sandy beaches,
and in life it is found l)uried in the sand a little below low-water
mark. Solemi/ia velum is a very pretty shell, covered with a
light brown radiated cjiidcrmis which projects far beyond the edges
of the shell, its margins being slit into numerous lobes. The species
is active, leajjing about with its foot, and swimming by ojiening and closing its valves.
A larger species is S. borealis, in which the lobes of the epidermis are iirojjortionately
much longer and narrower.

Tlie family Gastrocii.exid^, or Tubicolid.e, has a very heterogeneous appear-
ance, some of its members bearing close resemblance to the next family. The shell is
equi-valve and the hinge is toothless, and not infrequently, in the adult, the shells are
imbedded in a calcareous tube, so that the whole has but little resemblance to an
ordinary bivalve. In Gastrochama the valves are distinct from the tube, in Clavagelbi
one valve is fixed, while in Asjxi-ff ilium both valves are united with the tube, of wliicli
they foi-ni a very inconsiderable portion, as is shown in our figure. All of the nieni-

FlG. 310. — ^ulemi/ia
velum.

Fig. 311. — Aspergillum vaglntferutn, watering-pot shell.

bers of the family are borers, penetrating hard mud, shells, coral, or rock. The most
noticeable species is the ' watering pot,' Aspert/illum vaginiferum. Here the valves
are very small, while the lower end of the tube is closed below by a disc, which is per-
forated by numerous holes and short tubules. The other part of the tube is much
longer, and at its dist.al portion is surrounded by one or more calcareous ruffles, so
tli.it the whole has a very bizarre appearance. This species comes from the Red Sea,
and all other members of the genus belong to the Indo-Pacific region.

The PnoLADiD.E, taken in its widest sense, is a family characterized by the absence of
hinge teeth and of hinge ligaments. Instead, we usually find one or two accessory pieces
(pallets they are called) which, in the Pholadinte, lie between the valves at the hinge

284 LOWER INVERTEBRATES.

line, or, ns in the Teredinw, are liorne at the extremity of the long, calcareous tube
formed by these animals. The margins of the mantle are almost comjiletely united,
leaving only a small opening in front for the protrusion of the short and truncated foot.
At the other end it is prolonged into a very large siphon, which, in the I'eredos, has
the power of secreting a calcareous tube. The gills are long and narrow, and, pos-
teriorly, are drawn out into a point which extends some distance into the excurrent
siphon.

They are all lioring animals, and make their burrows, some in mud or sand, some
in submerged wood, while others bore into rocks, shells, or corals, at times doing con-
siderable damage to human interests. The distinctions between the two sulj-families
is sufficiently emiihasized in the foregoing paragraph.

The genus Teredo, with about twenty-five so-called species, has gained a some-
what extensive notoriety under the popular name of ship-worm, and hence deserves
some little attention at our hands. The Teredo is a long, worm-like animal, bearing
at the larger end a comparatively small bivalve shell, while near the other are the
two accessory pieces, the so-called ))allets, beyond which extend the separate ex-
tremities of the siphonal tubes. The development of the Teredo has been made the

subject of exhaustive papers by Quatrefages and
Hatschek, from which we learn that, like other
molluscs, it passes through a veliger stage. Soon
after this the young larva comes across a piece
of submerged wood, or, in case it does not, it
dies. At first it creeps over the surface of the
timber, but soon it settles clown and begins the
Fig. 312. — Young /'■;.-/„ before it begins excavations which are to result in that prison,

its burrow. .... ,, ., , .^

which It never leaves until death. iLxactly how
it excavates is still a matter of dispute, but it seems probable that it is jiartly by
means of the edges of the pallets. Another theory of action is that the foot, with its
thick coriaceous epidermis, cuts .away the wood. The hole made at first l)v the young
Teredo is minute, about as large as a pin's head, but, once within the wood, it grows
rapidly, and its burrow is enlarged in the same proportion. As it excavates farther
and farther into the wood, it lines its channel by a calcareous deposit, thus forming a
shelly tidie, which, on our coasts rarely exceeds ten inches in length and a quarter
of an inch in diameter, but in favored localities some species attain a length of
two feet and a half. In tliis tube the animal lives, its onlj^ means of communica-
tion with the external world being through the small hole by which it entered the
timlier.

The Teredo does not feed upon the wood, the small particles which it erodes being
passed out through the excurrent siphon. The food which nourishes the animal is, here
as elsewhere, brought in through the incurrent siphon, and consists of microscopic
animals and plants. Notwithstanding the fact that the Teredo does not eat the wood,
the damage it does is very great. It was first brought prominently into notice at the
beginning of the eighteenth century, when, by its ravages in the piles and other sub-
merged wood which supported the dikes and sea-walls of Holland, it seriously threat-
ened the safety of that country. Hundreds of individuals will obtain entrance to the
same bit of timber, and, boring either M'ith or across the grain, they soon convert it into
a mere shell, ready to break down at the slightest strain. The rajiidity witli which
they work is well illustrated by a fact recorded by Quatrefages. In the early sjiring

MOLLUSCS.

285

\
\

\\

Mm

i

an accident sank a coasting boat near St. Sebastian in Spain. Four months later some

lishermen raised the vessel, hoping to turn the materials to advantage, if not to repair

the vessel itself, but in the short space of time that had

elapsed, the planks and timbers were so completely riddled

by the Teredos that they were valueless. There is a curious

fact noticed in connection with their burrowing. No

matter how many of these molluscs gain' entrance to the

same piece of wood, their tubes never iiiteifere with one

another, but there is always left at least a thin j)artition

between two adjacent burrows.

Since their appearance in Holland so long ago, these ship-worms
have done an incredible amount of .damage to wharves, shijss, etc.,
and many devices have been suggested for cheeking their ravages.
The use of chemicals, creosote, etc., has but comparatively slight
effect, for since these animals do not eat the wood, the chemicals do
not poison them. While kyanising (soaking the wood with creosote)
is an effectual check against that injurious crustacean, the gribble
(Limnoria lignorum), it is but a slight defence against the Teredo.
In Xorway, timbers which were saturated with creosote under a
pressure of ten pounds to the square foot were found two years
later to be filled with the molluscs. To iron rust they have a de-
cided aversion, and piles and other timbers whieii are driven full of
broad-headed nails escape their ravages. Our modern vessels also

escape their injurious action, thanks to
the copper sheathing with which their
hulls are covered. On our coasts south
of Ca]ie Cod, it is customary to coat all
spars and buoys with verdigris paint,
and to take them up every six months
for cleaning and a new coat of this
poisonous paint. Notwithstanding this,
the average life of a buoy is only about
twelve years, but half of which is spent
in the water.

On our coast, Teredo navalis is the
most common and most injurious spe-
cies, but three other species of Teredo
and one of X^i/lotrya, an allied genus,
occur in larger or smaller numbers. In
tropical waters many other foi-ms occur,
of which we need only mention T.
corm'formis, which burrows in the
husks of cocoa-nuts and other woody
fruits floating on the sea, and the gigantic Septaria
arenarki, of the Philippine Islands, which burrows in
the sand, sometimes attaining a diameter of two inches
and a length of nearly six feet.

Pholas and its allies are also burrowing forms, but, unlike those just mentioned,

•i\

Fl( ul —TtLdofii-
talis, ship-worm.

Fig. 314. — Teredo navalis.

286

L 0 WER IN VER TERRA TES.

they do not form tubes, nor do they, except Xylophaga^ live in wood. In Pholas the
valves are large and the shells are never completely closed in front. The shell is long
and cylindrical, and the pallial sinus reaches to the middle of the valves. The com-
mon name for these
molluscs in England
is jiiddock, but no ap-
pellative has gained
much currency here.
The species bore in
sanil, clay, limestone,
and even gneiss.
Doubtless here the
^S instrument of boring
ig is the foot with its
hardened d e r m a 1
armor. When we
consider the hardness
of some of the rocks
])erforated, we can
scarcely realize that
this organ is suffi-
cient to produce the
effects, but time is a
matter of small im-
portance to tlie pho-
lads. As they increase in size they increase the size of the burrows, whicli are always
just a little larger than the shell. These burrows are always nearly vertical, and but
rarely encroach upon each other.

In Europe the piddock are esteemed a delicacj^, and on the coast of Xormandy
their cajiture furnishes employment to a good many women and children, who pull
them iwnw their burrows with an iron hook. They are usually cooked, Init are said to
be very palatal)le raw. One remarkable peculiarity of the pholads is their phosphores- .
cence or ca]iacity of shining in the dark, which is here better developed than anywhere
else among the Molhisca, unless it be in I'luUirlioe. The common Euroi)ean species is
Pholas dactylus^ while on our coasts are found P. coMkIu and P. trtiii(:af<i. A closely
allied genus, ZlrpliiiKi, has a species, Z. cr!s-
}Xtta, common both to Xew and Old England
and the nurthcrn waters between. In this
genus the shell is sliort and the accessory
valves are absent.

In another section of the family we iind
pholads in which the anterior gajie of the
shell is closed by a callous jilate. Here be-
long the genera Pholadidea and Jfartesia.
Martcsid smithii, on otir coast, burrows in oyster shells, while other forms have differ-
ent habitats. While most of the Pholadid.a> are marine, Adams reports finding a
species in the fresh water of Borneo, living in dead trunks of trees.

I IG 31o — Phokfi in It I'lir

/ J

Fig. ?M. -

i-w-jjala.

MOLLUSCS.

287

Class H. — CEPHALOPHOKA.

The remainder of the Molhisca differ greatly from the group wliicli we have just
left, and the fact tluit nearly all of thein possess a lingual ribhou (au organ to be
described furtlier on), while there is a head distinct from the rest of the body, has
caused them to be included in one large group, variously termed Glossophora, Odon-
tophora, and Cephalophora. In the present work, however, the term Cephaloj)liora
is restricted to indicate the forms between the squids and cuttle-lishes (Cejihalopoda)
and the AcephaLa.

The anterior end of the body is more or less distinctly marked off as a head, and
this differentiation is the more marked in many forms from the fact that it usually
bears tentacles and eyes, and thus is seen to he the locality of the senses, increasing-
its cLaim to the term head. The body jwssesses a bilateral symmetry, but, owing to
the fact that most of the forms live in spiral shells, this resemblance between the two
sides is somewhat obscured. The body is enveloped (at least in the young) in a
mantle comparable to that of the Acephals, which in most forms secretes the shell,
which is usually calcareous, but not infrequently, as in our common snails, is more or
less horny. As these shells are very important from a systematic point of view, and,
indeed, are the only portions usually jjreserved, they demand far more attention than
they otherwise would.

The shells of the Ceijlialojihora are always, except in the chitons, univalvular ; that
is, composed of a single jiiece, wliich, though ])resenting the most various forms, can in
reality be reduced to a simple type. This type is a cone. The cone may be broad
and low, as in the limpets, or it may be greatly drawn out and very slender, as in the
tooth-shells. It may lie coiled in a nearly fiat spiral, or it may be curled in a cttnical
spiral, the form found in most of the shells of the group.
In some few forms the shell is internal, lieing envelo]ied
in a fold of the mantle, while in a large number of these
animals no shell is present. In the chitons the shell con-
sists of a number of pieces, never more than eiglit,
arranged in a linear series on the back.

In systematic works each part of the shell has its
name. The upper spiral portion is known as the spire,
and the curved portions of which it is composed are
known as the whorls, the last and largest being the
body whorl. The whorls are separated from each other
l)y the sutures. The opening is known as the mouth
or aperture, the outer edge of which is the lip, the inner
the columella. Sometimes the lip is prolonged into one
oi- two grooves or canals which are always approxi-
mately parallel with the axis of the shell". The one fig. 317. -Parts of a gasteropod shell;

nearest the spire is the posterior, the other the anterior "i.^XT ^ui^r VrH moutl; <^
canal. Frequently an openino- is left in the axis of the aperture; p, posterior canal; s, sn-

"^ ^ ■"' ' " tures; sp, spire; «, iimbuicus,

shell, which is known as the umbilicus.

Returning to the animal itself, the next thing we have to notice is the foot, which
is usually large and muscular, and is used as an organ of locomotion. It may bear on
either side a lateral appendage (ejiipodium), while frequently on the dorsal surface of

288

LOWER IN VEU TEBliA TES.

Fig. 310. — Jaw of
Limax jlnrns.

the foot is a corneous or calcareous structure, tlie oiierculum, which is eiiiiiloyecl to
close the aperture of the shell when the animal retracts itself. The operculum may

be either horny or calcareous, and frequently shows a
spiral structure. Some of the calcareous opercula of
the smaller top shells are in common use as ' eye-stones.'
By the older conchologists it was sometimes held that
the Cephalojihora possessed bivalve shells like the
Acephals, the true shell being regarded as one valve,
and the operculum as the other. This view has been
shown to be erroneous, and now it is usually thought
that the ojierculuni corresponds to tlie bjssus of the
other group.

In most of the forms there is a chamber formed

Fig. 31^. — Melantho ponderosa partiiillv . -iiti li? n p ^

exteiiiied, siiowiiig the operculum (o) ou either Side ot the body by the tree edge oi the

on the upper surface of the foot. i ■ , i . i .. tt 1 1 i it- i i

mantle and tlie body itself. Usually the pallial cham-
ber on one side (usually the right) is larger than the other, and contains the gills when
these organs are present. It also contains the outlet of the alimentary canal.

The mouth is situated on the under side of the head, and is armed with variously
arranged jaws or plates of a hard chitinous or calcareous nature. Besides these, there
is found in all except a very few forms an odontophore, or, as it is
occasionally called, a tongue or lingual ribbon. This consists of a
ribbon-like band of chitin, attached at one end and free at the other,
and bearing on its upper surface numbers of hard, tooth-like processes.
The odontophore is attached to the floor of the mouth, and is moved

by appropriate muscles.
When in use it is drawn
over some sup]iorting
cartilages, and the teeth,
acting like a file, rasp
away the sulistance to
which the mouth is ap-
plied. The action can
le partly seen by watch-
ing pond snails feeding
upon the green slime
which frequently collects
on the sides of an aqua-
rium. The size of the
odontophore varies
greatly, as does also the
number of teeth. In some it is very long, in otliers it is more oval. The teeth them-
selves are arransjed in transverse series, there being in some species about two hundred
in a sino-le transverse row, while in others there are but three. By use this ribbon is
constantly wearing away at the tip, but the loss is compensated by a continuous growth
at the other end.

Within recent years the characters derived from the lingual ribbon have been
retjarded as very important in the arrangement of molluscs, but like all other good
thinffs this means of classification has been carried to an extreme; forms which in

Fig. 320. — Dingram of the mouth and lingual ribbon of a gasteropod; .;, jaw; m.
mouth; a, oesophagus; 7-, lingual ribbon; s, support of ribbon.

MOLLUSCS. 289

every other respect agree closely with each other being occasionally widely separated.
The characters derived should be compared with those obtained from other structures
and thus all such extremes would be avoided.

In most forms the body is distorted to fit
the spiral shell, and even where this is not
the case, the alimentary canal usually follows
a tortuous course, doubling on itself and
terminating usually on the right side of the
body, frequent! V in front of the nuddle. The
cavity of the mouth communicates with an ^'''- ''"'■- ^ TpMlallZtexta!^^"'''' '''''''°''
oesophagus which sometimes dilates into a

sort of crop, and eventually empties into the stomach, from which arises the intestine
either opposite to or beside the cardiac opening. In a few forms the stomach is armed
with plates or horny teeth. Salivary glands are almost always pi-esent, usually two in
number, but occasionally four are found, and it is interesting to note, in passing, that in
Dolium and some other forms these glands pour out a saliva containing sulphuric acid.
The liver is well developed.

The circulatory system is usually well developed, though in Dentalium a heart is
wanting, while other forms show a correspondence to the Acephals. Thus in the ear
and top shells, the alimentary canal perforates the heart, while in the first, as in the
chitons, there are two auricles. Usually, however, there is one auricle and one ven-
tricle, which propel a blood containing colorless, nucleated corpuscles. As in the
Acephals, the heart receives the blood from the gills and forces it to all parts of the
body.

Respiration is effected by means of gills or by pulmonary organs. The gills, which
are usually contained in a cavity of the mantle, may consist either of lamellar organs
or of plume-like brancliiaj. Lankester, who has recently investigated the structure of
the gills, is of the opinion that the primitive type was what he calls a ctenidium, con-
sisting of a central stalk to which lamellar res]>ir.atory processes were attached, a view
which seems open to some objections. The variations occurring in the respiratory
organs are of great vahte in systematic work, and will be referred to again in connec-
tion with the different grou])s. The pulmonary cavity of the Puhnonifera is formed
by a cavity of the mantle, and is richly supplied with blood vessels which extract the
oxygen necessary for respiration from the air. In a few forms special respiratory
organs are lacking.

Closel}^ connected with the organs of circulation are the renal organs. There are
one or more sacs near the heart and opening to the exterior, which extract their secre-
tion from the blood going to the heart, and convey it outside the body.

The nervous system acquires a different development in the various groups. In
the tooth shells it most nearly approaches that of the lamellibranchs, consisting of
two ganglia altove the oesophagus, connected by two nervous cords with a pair of
pedal ganglia, while two more cords connect the brain with two ganglia near the vent.
These two last are evidently comparable to the visceral ganglia of the bivalve mol-
luscs. In the other foi-ms the visceral ganglia may be increased in size and number,
and become closely connected with the other two pairs. The details of structure
should be sought in more technical works.

The auditory organs are usually seated near the ganglia of the foot. Eyes also
are generally present, and usually are two in number, situated upon the head or its
vol.. I. — 19

290

LOWER INVERTEBRATES.

appendages. The peculiar eyes of Onchidium and the chitons will be mentioned
further on. At the first glance the eyes of the gasteropoda (and also those of the
cephalopods) seem strikingly like those of the vertebrates. They liave an external
cornea behind which is a lens, a vitreous humor, and lastly a retina containing rods
and cones. A great difference exists in tlie fact that these rods and cones are on the
front side of the retina, and between them and the optic nerve is the pigment layer.
Frequently these organs are seated upon stalks or tentacles which are capable of
retraction. In our common garden snail may lie found an example of this structure,
and the retraction is accomplished by the drawing in of the end of the tentacle in the
same way that one inverts the finger of a glove.

The sexes of the gasteropods may be separate or combined in one individual, and
copulatory organs are frequently present. Blost forms lay eggs, a few, however, bring
forth living young, the eggs undei'going development witliin the parent. The eggs,
which are numerous, are frequently enveloped in cajjsules, differing greatly in form
and ornamentation, each capsule containing a number of eggs. We shall note the
appearance of some of the more interesting of these egg-cases in connection with
the forms to which they belong.

In the development of the eggs of the Cephalophora there is much diversity in the
early stages, according as the amount of food-yolk present is large or small. This
also intiuences the character of the gastrula which is formed, and the entoderm may
either be solid or in the form of a sac. Soon after the invagination, the outer surface
almost always becomes covered with cilia in certain regions, the most jirominent being
a ring around the body in advance of the mouth. This is the velum, so characteristic
of molluscs. At about the same time a small portion of the outer layer sinks in to
form the gland which eventually secretes the shell, and the foot begins to appear.
These changes all take place witliin the egg, and u))on the development of the

cilia, the larva begins to turn round and round, thus
rendering it difficult for the student to obtain a dis-
tinct view of what is going on inside the embryo,
or even to draw the external appearance. The .shell
gland begins to secrete the shell, which arises first
as a small plate, but soon takes the form of a cap
envelo]iing the jmsterior part of the body and
then gradually acquires a spiral form. The region
of the velum also exhibits a change. Instead of
being a I'ing around the Ijody it liecomes a two-
lobed plate fringed with cilia, which serve as loco-
motory organs after the young has hatched.

From this point the development is usually direct, no startling metamorphoses
being introduced. The velum almost always disa]ipears, and the body and shell
gradually acquire their adult structure. Still the variations and the changes under-
gone throw considerable light on the classification and arrangement of the different
forms.

The classification of the odontophorous molluscs is still in an uncertain condition,
notwithstanding the fact that they have been so extensively studied. In fact, there
are scarcely two authors who agree as to the rank and relationship of the different
associations of forms. This difference of opinion is partly due to the varying impor-
tance accorded to the different characters, and partly to the fact that a linear arrange-

FlG. 322. — Veliger of Eolis diversa.

MOLLUSCS. 291

ment does not exist in nature, there being numerous inter-relations between tlie different
groups. With this uncertainty it matters but little what classification we adopt,
thouoh that which follows seems to the writer to best rej^resent the present state of
our knowledge. All authors admit that the Scaphopoda are the lowest, while the
position of the Pteropoda is very uncertain, one of the latest writers including them
among the Cephalopods.

Sub-Class I. — Scaphopoda.

The tooth shells, as they are commonly called, are few in number, but their pecu-
liarities have caused them to be regarded witli considerable interest. They are of all
the Odontophora the most closely related to the Acephals. The shell is very long,
tapers sliglitly, and is either straight or curved like the tusk of an elephant, and is
open at both ends. The animal is attached to the shell near the smaller end, while
from the larger it protrudes a large number
of long and slender tentacles which are used
in obtaining food and as preliensible organs.
These tentacles arise far within the shell,
from a muscular ring surrounding the body. Fig. 323.-z)fHtaHHm removed from the siieii;/, foot;

» & J </, geuital organ; /, liver; Hi, mantle; ?(, kidney.

In advance of this ridge, but still within the

shell, is a cup, at the bottom of which lies the mouth. There are no eyes, no heart,
while the head is very rudimentary. The foot is large, three-lobed, and protrudes
from the larger end of the shell. The mantle is relatively very large and, like the
shell, is open at both ends.

The mouth is armed with a lingual ribbon, and the alimentary canal, which is con-
voluted, terminates Itehind the origin of the foot. The liver is large and two-branched,
and the sexes are distinct. There are no special i-es))iratory organs. We have already-
spoken of the nervous system.

The development of Dentulimn, which has been studied by Lacaze-Duthiers, is
very peculiar. After the formation of a morula, the body of the embryo becomes
surrounded with a number of rings of cilia, while at the anterior end is a tuft of
longer cilia. Gradually the anterior end becomes flattened into a disc, the edges of
which are ciliated, while the posterior part develops the mantle. This mantle secretes
the shell, which at first is open, but finally the edges of the mantle and the shell
unite, producing the tubular foi-m found in the adult.

The tooth shells are divided into two families (by S.ars accorded a higher rank),
founded on characters of the shell .and foot. In the first (Dext.u.iid.e) tlie margin of
the smaller end is entire, or has a medium ventral slit, while the foot is three-lobed ;
in the Siphonopoda the foot bears a circular disc, the edges of which are armed with
jiapilhe, while the posterior end of the shell is either entire or with numerous
notches.

The species are found in .all seas and live buried in the sand, the smaller end of the
shell protruding, and through this the water necessary for res-
piratory |)ur]ioscs is tlrawn. The large foot is employed in bur-
^''^' ?afe7tTO"ii'-"sheiT. ''"'' rowing, while the tentacles, which are ciliated, are employed in
ca])turing food, which consists of Foraniinifera and other minute
animals. About one hundred species are known, represented on our coasts by Den-
talium occidentale, Entalis striolata and three or four other species. The largest

292 LOWER INVERTEBRATES.

species is about four iuches in leugtli. The group of tooth shells first appears
in rocks of Devonian age.

Sub-Class II. — Gasteropoda.

This group, which contains by far the largest uuniber of forms (about twenty-five
thousand species being known), embraces the molluscs commonly known as snails,
slugs, sea-slugs, whelks, cowries, limpets, and the like. In all the liead is well
developed and bears one or two pairs of tentacles. The body is usually asymmetrical,
owing to the presence of a spii-al shell, though this is far from being invariably the
case. The alimentary tract is straight or doubled on itself, and usually terminates on
one side of the body. A heart is always present, except in the problematical form
JEntoconclui. Respiration is effected either by gills, by a pulmonary cavity, or by the
general surface of the body. The sexes are sejiarate in the majority of the foi'ms,
but are combined in the same individual in the Pulmonata.

The classification here adopted is based on that of Lankester, which, while it varies
greatly from that in common use, has the merit of agreeing well with our knowledge
of the anatomy and embryology of the group. The basis of Prof. Lankester's \>v\r
mary divisions is found in the symmetry or torsion of the body.

Super-Order I. — ISOPLEURA.

The name given to this division means equal-sided, which emphasizes the most im-
portant feature of their structure. They retain in the adult the primitive bilateral
sj^mmetry. The alimentary canal traverses the entire length of the body, and termi-
nates posteriorly in a median vent. Renal organs, gills, ciiTulatory organs and
genitals, are paired and symmetrical. The pedal and Aisceral nerve cords are straight
and parallel, extending the length of the body.

Order I. — CHiETODERM.E.

This group contains but a single genus, Chcetoderma, which \^•as originally placed
among the Gephyrean worms. C. nitidulum is a small, worm-like body, with an

enlarged head at one eiul, while the cavity of the
mantle is found at the other. In this small cavity
are a pair of small gills. The external integument
is roughened by minute calcareous spines, which
Fig. 325.- Chcetodermaniiiduium. ~ g've the body a hairy appearance. The foot is

obsolete, and the lingual apparatus is greatly re-
duced, the lingual ribbon being represented by but a single tooth. Xothing is known
of the embryology.

Order II. — NEOMENOIDEA.

Neonienia is a peculiar genus found on the western coast of Sweden. iV^ carinata
reaches the length of nearly an inch, grayish in color, with a shade of rosy red at the
posterior end of the body. The outer surface is covered with minute spines, giving it
a velvety apjiearance. In shape the body somewhat resembles a pea-pod, a dorsal
ridge giving rise to the specific name. The mantle is reduced to a small ring around

MOLLUSCS.

293

tlie vent, enclosino- tlie paired sjills. The lingual riblion is poorly developed, but bears
many teeth. The eggs pass out by the renal ducts. The mouth and pharynx can be
retracted or extended at will. The second genus of the order is
Proneomenia which has been found in the North Sea and in the
Mediterranean. It is more elongate and worm-like than Neo-
menia. Nothing is known of the embryology of either form.

Order III. — POLYPLACOPHORA.

Fig. 326. — iVt-omt-)i ia cnr-
inata, ventnil and side
views; a, anterior, 6, pos-
terior extremity; c, fur-
row in wliicll tlie foot is
concealed.

The chitons are a group which have made no little trouble
for zoologists. In the early days of science they, together with
the barnacles (which are really Crustacea) were united in a group
characterized by the possession of multivalve shells. More recently they have been
assigned a place among the gasteropoda, but here they have not
been allowed to remain in quiet, almost every author assigning
tliem positions of varying rank and relationship and one, influenced
by their peculiar development and the structure of the nervous
system, has actually placed them among the worms.

In external ajipearance the most striking feature is the serial
arrangement of eight calcareous shells upon the back, indicating
a segmentation far from common among the Mollusca. Thisseg-
mentntion is carried still farther, and we find the gills similarly
arranged on either side of the body (Fig. 328), to the number of
sixteen or more, each accompanied by an olfactory organ. Around
Fig. 327. — Chiton woss- the niarsi'in of the dorsal sm'face frequently occur calcareous spines,
or other forms of ornamentation useful in classification.
One of the most interesting of recent discoveries is that
the chitons, which have been so long studied and so long re-
garded as blind, are (in most genera) really very well pro-
vided with visual organs, the whole dorsal surface of some
forms being studded with eyes of which not less than eight
thousand occasionally exist on a single specimen. These
eyes are unlike the dorsal eyes of Onc/ndinni, and like those
on the tentacles of Helix, in that the retina is between the
nerve and the exterior. These eyes are further shown by
Professor Moseley to be developed from peculiar sense organs
covering the dorsal surface. No trace of these eyes has yet
been found in the fossil chitons.

The mouth is armed with a well-developed lingual ribbon,
in which the teeth are arranged in the following manner, —
5. 1. 1.1.5; the laterals being large and hooked. The in-
testine is coiled in a loose sjiiral and terminates in a median vent at the posterior end
of the body.

Little is known of the development of the chitons, but that little is very interest-
ing. Segmentation gives rise to a true gastrula and at the same time the velum is pro-
duced. At the anterior end a single flagellum is produced, which is soon replaced by
a tuft of cilia. Shortly a constriction appears behind the velum, and on the dorsal
surface appear six or seven transverse plates which may represent the shell glands.

Fig. 328. — Anatomy of Chiton ,
ao, aorta; br, gills; c, ven-
tricle; c', one auricle; g, ner-
vous ring; o, mouth; 0(1, ovi-
ducts.

294

LOWER TNVER TEBRA TES.

Two large eyes are also formed, which are remarkable in being behind the velum.
The details of the closure of the blastopore, the formation of the pedal nerves (of too
technical a character for recital here),
the bilateral symmetry and the segmen-
tation of the body, all point to the fact
that the chitons branched off from the
gastropodous stem at an early date.

The chitons are mostly

littoral forms living in the

sli allow w.aters of the

ocean. Over three hun-
FiG.33o.-rraoA;/- dred species are known ; but until the manuscrijjts of the late Dr. P. P.
redchUon? "^' Carpenter are edited and j)ublished, we shall have no adequate review

of the grou]). A large number of genera have been made, but with
these we need not concern ourselves.

Fig. 328. Development o£ Chiton.

Super-Okder II. — ANISOPLEURA.

In this, by far the largest division of the Gasteropoda, the symmetry so marked in
the preceding group is greatly obscured. The head and foot, indeed, retain the prim-
itive bilaterality ; but here the resemblance usually ends. The cause of this lack of sym-
metry in other parts of the organism is to be explained on mechanical grounds. On
the back there is usually developed a large shell, which, with its included viscera, ac-
quires a very great proportional weight. This shell naturally falls over to one side,
and by thus doing twists the various organs so that the ]n-imitively median anus occu-
pies a position at the anterior portion of the body, usually upon the right side, or may
even be placed in the median line above the head. Not only is the alimentary tract
affected by this torsion, but the openings of the kidneys, the gills, and other organs are
transposed, so that the gill, for in-
stance, of the normal right side is in
reality borne upon the left. Part of
the nervous system may or may not
share in this twisting, accordingly as
the visceral loop is above .or below
the anus. The effect of this twisting
is to coil the nerves in the shape of
the figure 8, and an illustration of the
stages of the process may be seen in
the adjacent diagrams copied from
Lankester who was first to jioint out
the systematic importance of these
facts. Coincident with this torsion
frequently occurs an atrophy of parts,
and, from the fact that the twisting usually occurs in one way, it is the gills, kidneys,
etc., of the left side which usually suffer or even entirely disappear.

The twisted or straight character of the visceral nervous loop gives a founda-
tion for a division of the Anisopleura into two groups, to which the names Streptoneura
and Euthyneura have been applied. To the former belong the -great majority of the

Fig. .131. — Diagram showing the torsion of the bojywhen the
visceral coiniiiissure passes above the intestine; A, nor-
mal condition; B, quarter rotation; C, complete half
rotation; a, anus; t, left, r, right renal organ.

MOLLUSCS.

295

aquatic and some of the terrestrial species, while the latter contains only the Opistho-
branchs and Pulmoniferu.

Oeder I. — OPISTHOBRANCHIATA.

This group is exclusively marine, and is composed of forms with a large foot, while
the visceral hump, so characteristic of most gasteropods, is very small, or wanting.
The name has reference to the fact that the gills are placed behind the heart, which is
but another statement of the fact that the torsion of the body has not been carried to
its full extent. In the adult stage some are provided with a shell, while in others this
is lacking; but all, without exception, have a shell in their earlier stages.

Fig. 332. — Circulation in Pleurobranchus auriantiacus, showing posterior position of the gills; a, mouth;
b, gill; ff, renal opening; h, heart; v, veins.

In some, gills are present, and may either i^roject freely into the water or be con-
cealed in tlie mantle cavity, while others have no specialized respiratory organs. The
position of the gills, mentioned above, has also its effect uj^on the cii'culatoiy organs,
and hence the auricle is here behind the ventricle of the heart. The vent is upon the
side of the body, and the sexes are united in the same individual. Two well-marked
sub-orders may be distinguished.

Sub-Order I. — Nudibranchiata.

Possibly no group of molluscs possesses more beautiful forms, or affords more in-
stances of protective resemblances, than does that which has received the name Nudi-
branchiata. Tills tei-m, which means naked
gills, is very approjiriate, for these organs,

when present, are not enclosed in a special ^ l] I /y

respiratory cavity, but project freely into the
surrounding medium, and are borne either on
the back or on the sides of the animal. Fi-om
the fact that in the adult stage no shell is
present, these forms are frequently termed,
in more common parlance, naked molluscs.
In the young stage a shell is jiresent. This embryonic shell, which is formed and
acquires a spiral or nautiloidal form before the young leaves the egg, disappears with
growth. It is transjiarent, and the young animal can close the aperture with an oper-
culum, while at other times it projects from the opening a ciliated velum, with which

Fig. 333. — Larva of Entocanclia.

296

LOWER INVERTEBRATES.

Fig. 33i. — Doris ftiSrfn, showing th
gills and a tent'acle enlarged.

it turns and swims as actively as any other gasteropod which retains its calcareous
armor throughout life.

The adult, however, is not always without protection other than that afforded by
its resemblance to the objects which it frequents, for in some forms the mantle secretes
calcareous spicules of various shapes, which sometimes are so numerous and so inter-
twined that, when the fleshy parts are dissolved in caustic
potash, they retain the positions they occupied when in
life. When these spicules are numerous, they cause the
dorsal surface to be roughened and hardened, forming a
protective dorsal shield.

As is implied in the foregoing, a mantle is sometimes
pi-esent, but in others this structure is not differentiated.
When present it is perforated, and through the openings
project the tentacles and the gills. In the young, well-
developed eyes are present, but in the adidts they appear
as minute black dots, just liehind the tentacles, or are ob-
solete. Tlie tentacles are prominent, and seem to serve as
olfactory organs, and not as organs of touch. Thej' are
frequently made up of a series of plates, presenting an
appearance which recalls the antennae of many insects ;
at other times thej' are plaited or simple, and not infre-
quently they may be retracted into trumpet-shaped sheaths near the base. These vari-
ations are of much imjwrtance in systematic work.

The gills, as we have said, are typically not inclosed in a cavity of the mantle, but,
when present, they project freely into the sea. They vary greatly in form and dispo-
sition, furnishing, in these respects, important systematic characters. Sometimes they
are in a more or less complete circle, surrounding the posterior opening of the aliment-
ary canal, or they may be ai'ranged in longitudinal series along the sides of the back or
body ; in the Phyllididse alone do we find any aj)})roach to the formation of a branchial
sac. In form they may resemble bushes, or they may be reduced to simjde papillte ;
all variations between these extremes being found. These gills perform but a part of
the respiratory economj', for, in all, the general surface of the body serves for the
aeration of the blood, and in the forms without gills it is the sole agent in this process.
The forms with gills are said to flourish when deprived by accident of these organs,
the skin performing their functions.

In the internal anatomy we find some points which deserve a brief mention. The
lingual ribbon varies in the number and arrangement of the teeth, according to the
family. The alimentary canal usually terminates on the right side of the body, though
in forms like Doris it may end medially. The stomach is surrounded by a large,
much-branched liver, portions of which extend into the elongated papilla, which are
found on the back. In the apices of these papillae are found thread cells, recalling the
similar defensive organs of the Hydrozoa. .

The nudilu-anchs are mostly littoral forms, and spend their lives creeping among
the rocks and seaweeds near the shoi-es. They can, however, swim, and, when em-
ploying this mode of locomotion, they usually progress with the back downward and
the foot uppermost. The food may be either vegetable or animal. Some forms feed
on the more minute alga\ while others create sad havoc among the hydroids. The
eggs are laid in bunches, upon stones, hydroids, or sea-weeds, almost every species

MOLLUSCS.

297

having its peculiar mode of oviposition. The eggs are imbedded in a transparent
gelatinous matrix, allowing the earlier stages of development to be readily seen.

Nearly one thousand species of nudibranchs have been described, from all seas ; but
as these forms have not been studied to the same extent as their shelled relatives, this
number will doubtless be greatly in-
creased by subsequent researches.

The first form requiring notice
is the peculiar Entoconcha mira-
bilis, whicli leads a parasitic life
inside the body of Si/najita, one of
the holothui'ians. So greatly has
parasitism altered the form of the
body, and all of the organs, that
the proper position of this form
among the gasteropods is far from
certain, some placing it near JVatica.
Indeed, were it not for the charac-
ters afforded by the young, its posi-
tion among the mollusca would not
be suspected. Some thirty years
ago Johannes Midler found m some
s])ecimens of Syna2:>ta digitata an
internal worm - like parasite, at-
tached by one extremity to the ali-
mentary canal, while the other end
hung free in the perivisceral cavity.
Other observers, notably Baur, have
investigated this strange form, but
there are many facts concernino; it iCj:
yet to be ascertamed.

In about one sjiecimen of *S'y«-
apta out of one or two hundred
this strange form occurs. It is n
sac, the uii])er ]>art bearing the
female and the lower the male re-
productive organs, while the cen-
tre of the body serves for a while
as a brood pouch, the em1)ryos later
passing out from an opening at the
free end of the body of the parent.
The eggs undergo a tolerably reg-
ular development, jiroducino; a
velum, shell, .-uid oiicrodum, the
later stages being found free in the
body-cavity of the host. After the stage shown in Fig. 333, nothing more is known of
their history. It would a)i])ear, from the little that is known of the development, and
from the characters of the embryo, that Entoconcha should possibly be assigned a place
among the nudibranchs. A second species of Entoconcha {E. millleri) is found in Holo-
thuria edulis. in the Philippines.

Flo. 335. — A, St/napta (Jif/itata, with parasitic Euforonckn, ua.t\lvaA
size; B, a portion of Si/na/ita with Eiitncovcha (F) enlarged; a,
point of attaclunent; h, blnoii vessels; /, female portion; i, in-
testine; )?j, male portion; me, mesentery.

298

LO WER IN VER TERRA TES.

Leaving these curious parasites, whieli, so far as known, are unrejiresented on our
shores, we come to forms which undoubtedly belong to the Nudibranchiuta, and which
lead free lives in the seas of all parts of the globe.

Passing by tlie Piivllidid.e, a small family of tropical and senii-troj)ieal forms, in
which the gills are either absent or enclosed between the mantles and the foot, we
come to the Elysiid.e, in which the body is shajied much like a common garden slug,

Fig. 33C. — Pontolimax capitans.

the gills have disappeared, and the tentacles are simple or absent. This family is
re23resented in our figures by PoiitoUmax capitans, a form onh' a third of an inch in
length, found on the coasts of northern Eurojie. It lives between tides, feeding on
minute alga?, and lays its eggs in small, pear-shaped capsules, each containing on the
average about one hundi-ed eggs. PontoUmax zonata occurs on the New England
coast. In Ehjsia, the typical genus of the family, the tentacles are well developed
and the sides of the body are expanded into a pair of wings, which stop just behind the
neck. Elysia viridis of the European seas is of a green color, as is also our New England
JE. chlorotica, and the closely allied Eli/siella catullns. These forms are not uncom-
mon, creeping about on the eel grass (Zostera) of our northern coasts.

7. — Elysia viridis.

In the EouD.E, a much larger family than the last, the gills, which may be
lammated, papillose, or like plumes, are arranged along the sides of the back, while the
tentacles are capable of being retracted into sheaths. The genus Tergij^es, which is
represented by a little species common upon the stems of hydroids, received its name
from old Forskal, from a belief that it walked u])on its back, using its gills as locomo-
tory organs. The braucliia? are eight in numljer, arrange<l in a single row of four on

MOLLUSCS.

299

each side. In Sermcea the gills are moi'e numerous, and the tentacles, which are
broad and flattened, are usually folded. Our New England species, H. cruciata, has
received its S23ecific name from the cross-like marking of each gill. The
species of Montagua, of which we have over half a dozen forms, and
the closely allied Eolis, have a large number of gills arranged in trans-
verse rows upon the sides of the back. They are very active animals
(for nudibranchs) and are common on piles of bridges, among the roots
of sea-weeds, and on rocky liottonis. They lay their eggs in gelatinous
spirals with wavy margins, resembling a lady's frill in general appear-
ance. Frequently bright colors are present, making these among the
most attractive of marine objects.

In Doto and allied forms the tentacles are retractile into cu2>shaped
sheaths, while the branchire are most curious bodies covered with minute
papilla?. Doto coronatu, which extends from our shores to those of fig. 338. — a«is
northern Europe, is a handsome object. It is scarcely more than half
an inch in length, Init, small as it is, there is room for spots of onmge, jiink, yellow,
carmine, purple, and white. Possibly one of our most striking forms is Dendronotus

arborescens, with its
curiously branching
gills, which, from
their thin, l)usliy ap-
]iearance, have given
rise to both its gen-
e r 1 c and sjiecific
names. This branch-
ing feature is also
seen in the tentacu-
lar sheaths which are
split up like the calyx
of a flower. The
general color is flesh-
red or brown. This
is one of the most
active of the naked
molluscs, and, when
confined in an aqua-
rium, is scarcely ever
quiet. It lies on

hydroids and sea-weeds, Iteing especially adapted for creeping around upon them by
its long and slender foot.

The genus Scyllea, which has the body exjianded into two long lobes, bearing the
gills on either side, is interesting from the fine instance of mimicry it affords. It lives
upon the gulf weed {SargasKiim) of the Atlantic and other seas, and with it is occa-
sionally drifted upon our shores. The large fields of this sea-weed which exist in the
tropical Atlantic have a fauna of its own, and among other forms are numbers of fishes,
crabs, shrimps, and the slugs now under discussion. Were it not for its protective
resemblance to the sea-weed on which it dwells, a resemblance embracing both form
and color, Scyllea jpelagica would furnish many a fine mouthful for its ^'oracious asso-
ciates, and the species would soon become extinct.

Fig. 339. — Dendronotus arborescens, bushy sea-slug.

300

LOWER IXVER TEBRA TES.

In Tet/ii/s \vc have another peculiar form embracing some of the largest of the
naked molluscs, 2\ Jimhriata, occasionally reaching a foot in length. Its general
, , aiiiiearance can be seen from our illustra-

' ''" "'^•' • tion, which, however, fails to convej- any

impression of the coloration of the animal.
It is nearly transparent, and covered with
dots and spots of red of different shades,
some so dark as to be almost black. The
curious gills on the upper surface were
once described as parasites. It is a )iative
of the Mediterranean, and, though often
captured, it lives but a short time in
aquaria, even in the large ones of the
Naiiles Zoological Station. It is a ra^
jiacious animal, feeding upon other mol-
luscs and small crustaceans.

In the remaining forms the l)ranchi8e
are arranged ujion the back in a more or
less complete circle which surrounds the
anus. As an e.vamjile of the Pulyceeid^
we may mention the beautiful Pohjcera
lessouii of our coast, with a pale, flesh-
colored body, flecked with bright green,
while the tentacles, gills, and tubercles on
the back are variously spotted with white
or yellow, and occasionally green. There
are several other American forms in this
family.
The PHYLLiEHOiD.f: is a very peculiar family, whose position among the molluscs

would not be certain were it not for the fact that it possesses a lingual ribbon.

PhijUirhoe bucejyhalus, the best known sjiecies, is a thin, compressed, translucent ani-

FlC. 340. — Te/ln/s nnihiinfn.

YiG.&n. — Phyllirhoe bucei>Ualus ; b, brain; //, heart: t, ii.testiiie; /.liver; m, moutli; r, reual organs; s, salivary

gland ; v, vent.

mal with a roun.le.l, fin-like tail, which swims freely through the water in much the
same manner as a tish. The head is furnished with two long tentacles, gills are absent,
and the intestine terminates on the right side of the body. Most of the specimens
bear a p.arasitic medusa, Mnestra parasitica. The most interesting fact connected
this animal is its phosphorescence. At night, when swimming in the sea or in an

MOLLUSC'S. 301

aquarium, when disturbed, its whole body is instantly illuniiiiated by points and dots
of light.

The DoEiDOPSiD^ is noticeable from the fact that the sjiecies, which in general
appearance resemble those of the next family, have a sucking mouth, and are desti-
tute of an odonto]ihore and jaw, thus presenting- a marked exception to all other
gasteropods.

The last and largest family of the nudibranchs is the Doeidid^, in which the ten-
tacles are laminate and retractile within sheaths, the shape of ^\■hich varies according
to the genus. There are about four hundred known species disti-ibuted in all the seas
of the world. The branchiaj vary considerably in shape, but are usually branched,
and w'hen expanded, the circle jiresents a close resemblance to a flower, the effect of
which is strengthened by the brilliant colors which are frequently present.

Species are most numerous north of Cape Cod. In their habits they resemble the
forms previously described. In Onchidoris the lower pair of tentacles are replaced by

Fig. 342. — Doris pitosn.

a broad membrane. In Doris the oral tentacles are distinct, and the branchiae, the
character of which is well shown in our illustrations, are capable of being retracted
into a cavity. Our si>ecies which are somewhat numerous, ap]iear in favorable locali-
ties in large numbers; but, owing to the protective coloration, which maybe similar to
the dull sea-weeds or the bright hydroids among which they dwell, they readily escape
the collector's eye. Other dark-colored forms are fi-equent under stones at or near low-
water mark.

Sub-Order II. — Tectibeanchiata.

The name for this group is the antithesis of that employed for the last, and is used
to indicate the fact that the gills are covered and concealed by a flap of the mantle.
The gills, it should be said in passing, are not homologous throughout the group. The
shell, which is usually present, is thin and delicate, and is not unfrequently concealed
by a flap of the mantle which is lieiit back over it. Another fact of importance is the
great development of the epipodia found in most members of the group. The eggs
are laid in long ribbons.

The first family we have to mention is the Tornatellid.e, which possesses an ovoid
spiral shell, which is usually marked with one or more sjiiral rows of punctures. The
body is large, but usually can be completely retracted into the shell. The cephalic
tentacles are large and broad, and united at the base, while the eyes are situated on

302

LOWER INVERTEBRATES.

tlie outside of tlie tentacles near their junction with the head. The shells are mostly
small, and jjossess but little interest ; a large proj)ortion are fossil, ranging from the
carboniferous to the present time.

The BuLLiD^ embraces much larger forms, in which the ventricose
shell is coiled in a spiral in which the spire is internal. The shell, in
many forms, is spirally banded or spotted, and is more or less concealed
l>y the mantle and epipodia. Th« lingual ribbon bears one median and
many lateral teeth. In Bulla the eyes are sessile on the middle of the
frontal fold formed by the united bases of the tentacles. The species
^^?e\la\7mmi!a^ frequent sandy and muddy bottoms near the shore, even going into
brackish water. At the retreat of the tide they burrow into the mud or
hide themselves beneath masses of seaweed. On our east coast is found B. solifaria,
a brownish spotted form. Cyliclma, which possibly deserves family rank, is repre-
sented on our shores by several small cylindrical shells which frequent slightly deeper
water than the Bullas. They move very slowly. Haminea may be readily separated
from Bulla by the lack of color in the shell.

FiG. 0-14. — Act,t\i hidUita.

In the PhilinidvE the bases of the tentacles are united to form a broad eejihalic
disc. The shell, which is covered by the mantle ami epijiodia, is shaped like that of
Bulla, but scarcely forms a single whorl ; in some it is internal and in others external.
Eyes may be present or absent. The species are found in water of moderate depth,
many species of Philine frequenting the shallow water along the shores.

The Aplysiid^ embraces slug-like forms known in popular parlance as ' sea-
hares.' The shell is small or wanting, and 'when present is covered by the mantle.
The stomach is armed with hardened teeth which ]ilay no unim|>ortant part in prepar-
ing the food for digestion. The animals feed principally on other molluscs, especially
on species of Acera (one of the Bnllidae). Apb/sia, the principal genus, has a pointed
oval shell, and the ejnpodia are extended in swimming. In one species (A. camelus)
numerous small glands are found beneath the free edge of the mantle which secrete
the purple for which these animals were celebrated among the ancients. Near the
base of the gill is the outlet of a gland, the secretion of which is said to be poisonous,
but whether any of the sea-hares have the toxic effects attributed to them, or even
have any poisonous qualities, is yet to be determined. Certain it is that all of the
group are not jioisonoiis, for one species forms an article of diet among the South
Sea Islands. Some of the European species have a very nauseous smell.

MOLLUSCS.

303

About sixty species of Aplysia are known from the whole world, though none are
found on our northern coasts. On the Portuguese shores they exist in large numbers,

-Ajih/sia tlepilanSy sea-liare.

and occasionally an easterly storm will throw them up in such quantities on the beach
as to cause an epidemic of sickness as well as to render the extraction of the purple
a matter of economic importance.

The last family of the Opisthobranclis to lie mentioned is the Pleueobranchid^,
represented on our coasts by the recently dis-
covered IiToousia obesa. In all the members
of the family the upper jaw is wanting, the
stomach very complicated, .anil dlxiiled into
several compartments. The shell, wliich is
usually present, is either borne on the back
like that of a limpet, or it is concealed as in
the typical genus PleurohrancJtus. These
forms, when creeping slowly through the
water, remind one of turtles, and in some
the resembhmce is .strengthened by the dis-
tribution of color. In their living state most
of the forms are very handsome. UmbveUa
is an aptly named genus, for the shell which
covers the back bears no little resemblance to the familiar object bearing the same
name.

Order II. — PULMONATA.

The Pulmonata or Pulmonifera is a grou[) of terrestrial or fresh-water molluscs in
which respiration is effected by means of a lung or pulmonary sac, no gills being
developed. All the members are herma]ihroditic, and an operculum is never formed.
Not all the land and fresh-w.ater gasteropods are here included, for, as we shall see
further on, many families which liave the same habits are entirely at variance with
the Pulmonata in the essentials of structure — most prominent being, that, in the one,
the visceral nervous loop is straight; in the other, a twisted condition is found.

Fig. 3411. — PU'itrobrttHchus pcronlL

304 LOWER INVERTEBRATES.

The pulmonary sac is formed by tlie union of tlie edge of the mantle to the body,
leaving a small round or oval entrance to a large sac, richly supplied with blood-ves-
sels. In most of the order this lung serves for breathing air, even in the aquatic
forms. The operation can readily be witnessed in such a form as Limncea, when kept
in confinement. At nearly regular intervals the snail will creep to the surface of the
water, and force a bubble of aii- out of the respiratory orifice, then more air is taken
in, and the snail descends again to its pastures. Recent investigations on the Lhnneans
from the profound depths of some of the Swiss lakes have shown some interesting
features in connection with this lung. Of course, snails living at these great depths
could not ascend to the surface for a supply of air, an<l it was found that they had
acquired a capacity of breathing the oxygen contained in the water, although no gills
were present. It is also interesting to observe that all the fresh-water pulmonates
fill their lung sac with water in the younger stages, and only later do they adopt
the aerial respiration. The pulmonary sac also subserves another function ; it
forms avery effective hydrostatic apparatus, as, by variations in its size, and con-
sequently in the amount of air, these animals are enabled to rise or sink in the water
at will.

The opening to the pulmonary chamber is, of course, at the edge of the mantle and
hence, as tliis jiart of the body is subject to considerable variation in size, the respii'a-
tory opening is far from constant in position. In the common snails (i/e^w-), for in-
stance, it is on the right side of the body, just within the shell as the animal is crawling
along, while in Testacella, where the mantle is very small, it is found near the posterior
end of the body. Even the side of the body on which the resjiiratory orifice is placed
is not constant ; in most it is found on the right side of the body, but occasionally it
occupies the median line behind.

Even greater variations are fouml in the shell. In some it is large enough to contain
the whole T)ody when retracted, some have it reduced to a scale-like plate on the sur-
face, others have it small and internal, while in still
others it is entirely absent. Usually it is coiled in a
spiral the whorls of which are dextral (revolving from
left to right) but in some genera the I'everse is the
case and the shell is wound from right to left. Even
in those which are normally dextral, sinistral mon-
strosities occur. It is a common idea, but an utterly
erroneous one, that the shells north of the equator are
coiled in one direction, and south of that line in the
Fig. 347.- ffl.iimmfEaeMes a dextral; other, the coil of the shell following the sun. A little

b, Phrjsa lorda, a sinistral shell. ' »

investigation of our fresh-water shells will produce
evidence utterly contradicting this. Only in the family Amphibolidie is an operculum
formed, but the other members of the order secrete a mucus which hardens and tightly
seals the aperture of the shell. This is known as the epiphi-agni and is formed when
the animal retires in winter or in a season of drought. On the return of moist weather,
it is broken down and the snail resumes its wanderings. In Clausiliu this e]ii])hragm
is a ]iermanent structure and is fastened to the mouth of the shell by an elastic stalk,
so that it works as a spring door.

The lingual ribbon is sliort and broad, and is armed with rows of very numerous
teeth, there being sometimes over two hundred in a single row. Each tooth has a
broad base and acute or denticulated recurved ti]is. This ribbon is opposed in some

MOLLUSCS.

305

forms by an upijer jaw composed of either one or three pieces ; in others, no upper jaw
is present.

The generative apparatus is rather comjilex and affords good systematic characters.
The most noticeable feature is that from the ovo-
testis a single duct proceeds, which afterward
divides into two tubes, one connecting with
the male, the other with the female copulatory
organs. In the Helicida^ jieculiar crystalline,
fluted, chitinous, or calcified rods or darts (sjoj'c-
ida amoris) are formed, the functions of which
are still problematical.

The eggs are laid in moist places, in damp
earth, under dead leaves, etc. ; or, by the aquatic
species, in the water. Those of Liimueu and
Planovhis are easily studied during their devel-
opment. In Limax, — tlie eggs of which are
laid sejiarately, each one resembling a drop of
dew — when the embryo is far along in its de-
velopment, a jjeculiar pulsating sac is formed
in the middle of the foot, the function of whicli
is as yet unknown.

Sub-Okder I. ' — Basomiviatophoea.

The position of the eyes affords a good char- fjg. ^S.-Embryo of Umax; d, yolk; e, eve;

acter for a division of the Pulmonata into two ^iiet'iiilMli^^Imi&J'oftS^
sub-orders. In the present group the visual granules.

organs are seated at the base of the solid, contractile feelers; the velum of the larva is
retained in the adult ; and the male and female generative apertures are separate and
placed on the right side of the neck. Most of the members of the sub-order are aquatic
in habits, though some lead more or less terrestrial lives.

The family Amphibolid.e, which occurs only in the New Zealand seas, serves to
connect the pulmonates with the opisthobranchs. They live in the salt marshes,
where the water is at least brackish, but are partially aerial in their respiration, although
rudimentary gills are jiresent. The shells are closed by a horny operculum. In
these two features the Amphibolidie differ from all other pulmonates. The shell is
spiral and thick, the spire short and the whorls shouldered. The native New Zea-
laiiders eat the animal.

The families Gadixidje and Siphoxarid.e embrace together about a hundred
species of limpet-like pulmonates, with shell and habits nearly like Acmcea and Patella.
No species are found on the east coast of the United States.

Concerning the AuRicuLiDyE more can be said. The animals are mostly tropical;
still several small sjiecies are found even in the northern states. The spiral shell is us-
ually thick and solid, and covered with an epidermis. The spire is short, the body
whorl large, and the outer lip is thick and frequently armed interiorly with teeth
which considerably contract the aperture. Similar teeth are found on the columellar
lip. The respiratory pore is posterior, and the male and female reproductive organs are
widely separated. The mouth is armed with a horny jaw.
VOL. I. —20

306

LOWER INVERTEBRATES.

The Auriculidai are mostly found in the neighborhood of the sea, especially in salt
marshes. The genus Auricula, from which the family derives its name, has but a verj'
remote resemblance to an ear ; the species are all inhabitants of
brackish-water swamjjs in tropical regions, and are characterized
by an absence of teeth on the outer lip of the long and narrow
aperture. In Scarabus the shell is laterally compressed, so that
the edges are angular ; the aperture would be large were it not for
the teeth which arise from both lips, and the sjiire of the shell is
acute. The species all come from the tropical parts of the eastern
hemisphere, where they live in the woods near the shore.

Alexia is represented in the United States by a single species,
A. myosotis, which does not extend farther south than New Jersey.
In Europe it is found on the shores of the Atlantic and the Medi-
terranean. It frequents places where it is covered by the tide for

Fig. 349. — Scarabus
fascialus.

Scaraf'Uti imbrinm.

Fig. 351. — Al-
exia myosotis.

several hours each day, moving in
a very sluggish manner. Fresh
water kills it. Other species are
found in Europe and the West
Indies. The shell is of a general
dark liorn color and bears two
tooth-like folds on the columella.
Caryck'mtn is much like Pupa in
shape, and our single species, C. e.v-
igmcm, is widely distributed under
stones and moss in damp places,
and is the only member of the

family which in the United States is found far from the sea.
iA In the sjjecies of Melanvpus the shell is ovate in outline, the spire

short, and the outer lip acute. Four species are found in the United
States, one on the Pacific and three on the Atlantic coasts. One of
the southern forms has received the specific name coffea, from its re-
semblance in size, shape, and color to a kernel of coffee. This species and an-
other, M. flames, occur in the United States only in Florida, except
when introduced elsewhere by means of vessels trading with southern
and West Indian ports. The remaining s|)ecies, M. bidentatus, is com-
mon in the grass of every salt marsh from Massaclnisetts to Texas.
When young, this is a very pretty species, being brownish in color,
marked with revolving reddish b.ands, .and the whole highly polished ;
but the adults are dirty and eroded. • The length of a large specimen is
about half an inch.

^ The species of Cassidida have a subquadrate body whorl and very

i\\\ short s]iire ; and the outer and inner lips are toothed. The species all

%/j belong to the Indo-Pacific region, frequenting mangrove swamps and

rocky shores. The species of Pedipes are all tropical and sub-trojncal.

They have a looping gait like that of a measuring worm, and with this

peculiarity in locomotion is correllated a tr.ans\'erse groove on the foot.

The members of the genus are among the most active of molluscs. No species occur

in the United States, the nearest approach being Lower California, where P. lirata

Fig. 3.'i2. — Cary-
chium exifjtmm.

Fig. 363. — Me-
lamjms biden-
tatus.

MOLLUSCS.

307

occurs. Otina is not represented in the United States. The shells are ear-shaped,
and colored, and the animals have the same method of locomotion as Pedqjes, living
among rocks between tide-marks.

All of members of the Limn.eid^ or pond-snail family are inhabitants of fresh
water, and, so far as investigations show, are most numerous in temperate regions.
Over six hundred nominal species exist, which belong largely to the genera Planorbis,
Physa, and Limncea. The shells are very variable in shape, but, with but little expe-
rience, one readily recognizes the members of the family. In some, tlie shell is a long

Fig. 354. — Different forms of Llmnosa elodes,

spiral, others have it coiled like a bit of tape, while still others have a shell without
trace of spiral, but flattened and limpet-like. Each of these three tyfies of shell is
regarded as affording characters of sub-family rank, and we have the Limnaeinse,
Planorbinaj, and Ancylinre respectively.

The pond-snails are exclusively vegetable feeders. They frequent the still waters of
sluggish streams and ponds, their thin shells being poorly adapted for a life in rapidly
running creeks. They usually require to go to the surface to breathe, but, as noticed
on a previous page, this is not always the case. The eggs are laid in clusters attached
to sub-aquatic objects and imbedded in a gelatinous matrix. Frequently specimens
may be seen progressing at the surface of the water shell downwards, the bottom of

Fiu. 355. — Livinwa stagnalls, pond-anail.

the foot being just above the liquid. An interesting fact, first pointed out by Pro-
fessor E. Ray Lankester, is that in this family the velum persists in the adult, nearly as
lai-ge relatively as in the veliger stage. Though these forms have been much studied,
this fact escaped observation until 1883.

Fii'st in order comes the genus Limncea with a thin, horn-colored, slender, spiral
shell and a large aperture. Important in separating this from the next genus to be
mentioned is the fact that the shell is always dextral, that is, the whorls revolve from
left to right. In times of drought the Limneans burrow into the mud and close the

308

LOWER INVERTEBRATES.

Fig. 356. — Limncea
megasoma.

aperture of tlie shell with an epiphragin like that of the Helicidns, thus preventing any
desiccation of the fluids of the body. When the rains again till the ponds, they come
out of their burrows and lead a fi-ee life. Of the species but little
can be said, and we will let our figures speak for themselves. All
figured are from the United States, though several are found in
Europe as well. Doubtless, when these forms are studied in the
proper manner, by rearing in confinement all of the jirogeny of
a single pair, and continuing the operation for several generations,
it will be found that many of the so-called species are but vagaries.
Indeed, Mr. P. R. Whitfield has done this with sjiecimens of Lini-
ncea megasoma and has found that, in this way, variations were
produced, which conchologists, not knowing the history of the
group, would describe as distinct species. Mr. Whitfield's experi-
ments however, were not conclusive, as there was a]i|inrently a
lack of nutrition and a higher temperature than the normal,
which doubtless had an effect on the forms produced.

Limmea is essentially a northern genus, reaching its highest
development in North America, in the British possessions ;
Physa on the other hand, is more southerly. It has a thin,
amber-coloi'ed shell, the whorls of which revolve from right to
left. The species are much more active than those of Limiuea.
The tentacles are long and slender, and the jaw is formed of a
single piece. Twenty-three so-called species occur in North
America.

The genus Pompholyx is noticeable, from the fact that,
while the shell is dextral, the genitalia open on the left side
of the body. The shell is short and broad. Three species are
known, all from the Pacific region of the United States. They were formerly supposed
to have two pairs of eyes.

In Planorhis the shell is wound in a fiat sj)iral, like a roll of tape,
showing the whorls on either side. The animals jirefer still water,
where they move about in a sluggish manner. About a hundred and
fifty s|iecies have been described, of which about twenty-five occur in
the United States. Any description of the various forms would prove
tiresome reading for any but the systematic student.
The species of Ancylits and GumllacJiia are shaped nearly like the limpets Acmcea
and Crepidula, and, judging from the shell alone, one would not realize
that the animals were so distinct. These fresh-water limjiets have the
same habits as their marine equivalents. They live attached to the
under sides of stones below the surface of the water, feeding on con-
ferva and other plants. In both, the body is sinistral, the genital open-
ings being on the left side of the body. In Anci/lus, of which we have
about twenty species in the United States, the shell is not at all spiral, but in Gund-
lac/iia it resembles Crepidida in this resjiect. Two sj)ecies of the latter genus are
found within our boundaries, the three remaining species being from the West Indies
and Tasmania.

The fresh-water jiulmonates are badly infested with parasites, most of which ai'e
stages of worms which reach their complete develojmient in some of the vertebrates.

Fig.

. — a, J'lii/sa ampul-
lacea; b, P. e'longata, c,
P. heterostropha.

Fig. 368. — Plan-
orbis.

Fig. 359. —^n-
ci/lus.

MOLLUSCS. 309

On a preceding page has been detailed the history of the liver-fluke, Distoma, which
passes a portion of its life in a species of X,inm'ra, and this is far from a solitary
example. These snails are eaten by fishes and birds, and in the stomach of the eater,
tlie larvcB are set free, and enter into a new stage of existence. In some few cases
the history has been thoroughly worked out, but in the majority there is a field for
investigation, which will give the careful student wonderful results. The subject is
difficult to studv, but, with time and patience its problems may be solved.

Sxjb-Order II. — Stylommatophora.

The gi-eat majority of the Stylommatophora are terrestrial, and are readily distin-
guished from the other sub-order by having two pairs of tentacles, the superior pair
bearing the eyes at the extremity. These tentacles may be simply retracted, or, as in
the common snails the tip can be turned in like the finger of a glove, a condition de-
scribed as invaginate. In most of the sub-order the
genital orifices are united.

The first family to be considered is the Onchidiid^,
which embraces a few terrestrial and aquatic forms from
warm latitudes. They have the male and female orifices
widely separated, and the eye-bearing tentacles simply
contractile and not capable of being invaginated. No
shell occurs in the family. Onchidium has been ren-
dered prominent by the researches of Semper. This
naturalist studied one of the species found in the eastern
seas, and found that, besides the eyes borne on the end
of the tentacles, the whole dorsal surface was covered
with visual organs, a fact which will recall the more re-

-,. . fTri •! T , !• Fig. 360. — OncAifiiiim tonganum.

cent discoveries of iVloseley with regard to the chitons.

These eyes are different from those borne on the tentacles in the fact that, in struc-
ture and development, tliey are like those of vertebrates, the nervous fibres penetra-
ting the layer of rods and cones, and being distributed over their inner surface.

Whether these eyes exist in all species of Onchiduim is not known, as all have not
yet been made the subject of proper histological investigation. Why these eyes
should be developed here is uncertain. The only explanation as yet advanced is that
of Semper. The 0)ichhKa live on the shores of the ocean, where they creep about in
a slug-like manner. They play an important part in the diet of the jumping fish,
Periophthalmus., which leaves the water and travels about on the beach left bare by the
retreating tide, looking for food. Semper supposes that these eyes are of considerable
use in avoiding this enemy of the race.

The genera Onckklella and Peronia are also marine and live on .algae. They are
amphibious, and if ke])t moist, they can live for a long time removed from the water.
Veronicella is a terrestrial genus represented by a single species in Florida, and several
others in the tropics of the old and new worlds. They live in families under trees and
stones, whence they come forth at night, ascending trees, etc., in their search for food.
Unlike the slugs, which they resemble in general appearance, they leave no slimy tracks
behind them. They lay their eggs in long gelatinous threads', fifteen or twenty being
contained in a single string.

In all the remaining families the generative orifices are united, but the question of

310

LOWER INVERTEBRATES.

Fig. 361. — Testacella haliotklca.

what constitutes a family here is not yet settled. We have endeavored to take a con-
servative course in this respect, and hence but few families re2:)resent the many divi-
sions which exist in some systems. The first is the Testacellid^, in which the animal
is like the familiar garden slug, but bears a small shell on the hinder end of the body,
and the mouth has no upper jaw. The genus Testacella is European and is noticeable
from the fact that it forms an exception to the other pulmonates in being predatory

and carnivorous. Its prin-
cipal diet is earth-worms.
It lives beneath the surface
of the earth, and follows
the worms down their bur-
rows. Other articles of food
are snails and slugs, and it
will even eat its own spe-
cies. It, however, wants its
prey alive, and even refuses
jiieces of a fresh worm which
has been cho]iped up to feed
it. Many tales are told of
its ferocity and cunning. They are said to live for five or six years ; at the approach
of cold weather they burrow deep into the earth, and, with the mucus they secrete,
they form a cocoon in which they spend the winter.

Allied to Testacella., but still entitled to family rank, is a grouji which is called
Oleacinid.e. As in the last family, an ujiper j.aw is wanting, but the shell is much
better develojsed and cap.able of containing the body when retracted. Most ]>rom-
inent is the genus Glandiiut, \vith about a hundred and twenty-five sjiecies. It has a
fusiform shell with a thin, sliarji, outer lip. Glanclina truncata, our best known species,
extends from South Carolina to Texas, and possibly further south. It prefers moist
situations, and thrives in tiie Everglades of Florida, living in humps of coarse grass. It
is partially if not wholly carnivorous, but, unlike Testacella., it is not averse to dead
animal matter, and will eat that which is partially decayed. It is even cannibalistic.
Its tongue is armed with numerous long, sharp teeth, with which it rasps off large
mouthfuls of its pre}'. The shell is usuallj' ashy fawn color, more or less tinged with
pink, which soon fades after death. In a Central American species, G. rosea, the
color persists to a much greater extent. Some of the South American species are
much more predacious than our forms, and do not hesitate to attack snails as large
or larger than themselves.

In StrejJta.vis, a South American genus, the shell is more like that of the normal
species of Helix (to be described below), but there is a curious distortion. The axis
of the shell is bent so that the lower whorls are not parallel to the earlier ones.

The American family CvLixDEELLTn.E needs but a passing mention. The shell, as
the name indicates, is .shaped like a cylinder, composed of many whorls, the last being
usually more or less detached from tlie others, and terminated by a circular mouth.
The animals have sluggish motions, and drag their sliell horizontally behind them. A
few species are found in Florida, but the family reaches its highest development in
the tropics, especially in the West India Islands.

The Heijcid^ is by far the largest family of pulmonates ; indeed, it contains more
species than all the other families together. Over sixty-five hundred species have

MOLLUSCS. 311

been described. A concise definition of tlie group is impossible, yet all of its mem-
bers are readily recognized by the tyro as belonging to the family. There is an in-
describable somethhig which at once tells the student that the specimen before him
belongs to the family Helicida\ Still, notwithstanding the fact that we cannot frame
a satisfactory definition, it will be well to review a few of the characters found in the
group.

In all, the upper jaw is present and opposable to the lingual ribbon ; the tentacles
■which bear the eyes are longest and can be invaginated. The shell is spiral, usually
well developed, and capable of containing the whole animal ; the reproductive orifice
is near the base of the right ocular tentacle. An immense number of genera and sub-
genera have been made in order to render the identification and classification of the
numerous species an easier task. Even the family Ilelicidje has been broken up into
divisions, each of which have been accorded family rank, but which here are regarded
as sub-families. Space and the ])atience of our readers will allow l)Ut the mention of
but a few forms, while our illustrations will show the general appearance of many of
the species found in the United States, as well as a few from foreign countries.

The Helicida3 are all terrestrial, herbivoi'ous animals, which delight in woods, es-
pecially in limestone regions. In Europe, some si)ecies have proved ^ „ ^
themselves nuisances to the agriculturist, but with us they have not ^ ^ \_j?^
yet done much damage. Our American forms seem to avoid culti- ^^^"^^^^^y
vated places, and the little damage done the farmer or gardener by ^'*^- ^,^fj;,^,f°""^'
the molluscs is occasioned by the slugs {Limax) and a few imported
snails. Why there should be this difference between the snails of Europe and America
is not easy to say ; possibly it is because our native species have not yet had time to
adapt themselves to the changed conditions which accompany civilization ; and they
still adhere to the traditions of their fathers.

The land snails possess great vitality, and as an illustration we cannot refrain from
quoting the wonderful history of a specimen of Helix desertorum, which has figured
in many a work on the subject of the Mollusca. This specimen was brought from
Egypt to England. It "was fixed to a tablet in the British museum on the 25th of
March, 1846; and on the 7th of March, 1850, it was observed that he must have
come out of his shell in the interval (as the ]iaper had been discolored, apparently in
his attempt to get away) ; luit, finding escape impossible, had again retired, closing
his shell with the usual glistening film ; this led to his immersion in tepid water and
marvellous recovery." Even longer was the life of a specimen of Helix veatchii, from
Lower California, detailed by Dr. R. E. C. Stearns. This individual lived six years,
from 1859 to 1865, in confinement, without food.

The time of oviposition is from April to June. The number of eggs varies from
thirty to fifty or more. They are laid in the light, moist mould, each one separate, or
united by the slightly adhesive exterior. There is no gelatinous matrix like that
found in the aquatic forms. In laying the eggs, the snail usually burrows its head into
the soil, stretching the body to the utmost extent. Since the reproductive orifice, as
has been said, is beneath the upper tentacles, this places the eggs at a distance beneath
the surface about equal to the length of the body in front of the shell. Other species
actually burrow beneath the surface to the dejjth of three or four inches before laying
their eggs, so as to insure a moist condition.

It is related that the eggs possess great vitality, and that they are capable of with-
standing desiccation. When so dry that they had lost all form, and were reduced to

312

LOWER INVERTEBUATES.

a friable condition, an exposure of but a single hour to moisture restored tbeir former
form and elasticity, and the egg developed in the normal manner. The writer, in his
studies of the development of Z,iniax, did not have such results. The eggs, after
drying, were readily swollen by a moist atmosphere ; but if the desiccation had been
too long continued (even witliout heat), the eggs failed to develop farther.

Like most of the shelled pulmonates, the Helicidaj in temperate climates form an
epiphragm to close the shell during the winter hibernation, and in the hotter portions
of the globe during the dry season. The method of forming this has thus been de-
scribed. " The animal being withdrawn into the shell, the collar is brought to a level
with the aperture, and a quantity of mucus is poiired out from it and covers it. A
small quantity of air is then emitted from the respiratory foramen, which detaches the
mucus from the collar, and projects it in a convex form like a bubble. At the same
time the animal retreats farther into the shell, leaving a vacuum between itself and
the membrane, which is consequently pressed back by the external air to a level ^^•ith
the aperture, or even farther, so as to form a concave surface, where, having become
desiccated and hard, it remains fixed. These operations are nearly simultaneous, and
occupy but .an instant. As the weather becomes colder, the anim.al retires fartlier into
the shell and makes another septum, and so on, until sometimes there are as many as
six of these partitions ; the circulation becomes slow ; the pulsations of the heart, which
in the season of activity vary from forty to sixty in a minute, according to the tem-
perature of the air, decrease in frequency and strength, until they at length become
imperceptible ; the other functions of the body cease, and a state of torpidity succeeds,
which is interrupted only by the heat of the next spring's sun." With the snails which
occupy a constantly warm, moist climate like that of Florida, there is no period of
hibernation ; they are active throughout the year.

First in order comes the Vitrininse, of which tlie genus Vitriim is the type. Here
the thin spiral shell is too small to contain the entire animal, and is
composed of a few rapidly enlarging whorls. The species are very
active and live in moist situations, usually feeding on vegetable sub-
stances, but not in all cases being averse to an animal diet. Thi'ee
species of this genus are found in the United States, while there are
about a hundred in the entire world. The most common form in our
territor_y is that figured, TT ixlluckla.

In the next sub-f.amily, the Zonitinse, but two genera need our
attention. In the genus Macrocydis, of which only one species is
found east of the Rocky Mountains, the thin shell has a wide um-
bilicus and a sharp outer lip. M. concava is comparatively common
and leads an active life. It is very voracious, and feeds upon other
species of the family. Its body is narrow and
very extensible, and it thrusts it into the shell of
other species and feeds on the soft parts at its
leisure. Zonites contains many more species than tlie genus just
mentioned, in which the shell is much like that in Mucrocijclh, the
differences being found almost entirely in the dentition and in the
soft parts. Z. cellaria is an Eurojiean species which has been in-
troduced into America, where it is now common in the seaport
towns along the Atlantic coasts. It lives in cellars and in hothouses and gardens.
The way in which it has been introduced is uncertain. From its habits it would

(^

Fig. 363. —Fiorina
peliucida.

Fk St 4 — l/( iny~
clii> toncaia

Fig. :im. — Zonites cel-
laria, cellar snail.

MOLLUSCS.

313

Fig. BUi;.

appear probable that it came along with hothouse plants, or that its eggs may have
adhered to some wine cask and found suitable conditions for development in the
cellars of the new world. Many other species are found in the United States, most of
them being small and inconspicuous, Z. milium being one of our smallest shells.

The genus Helix lias been divided into innumerable sub-genera and tribes, the de-
tails of which should be sought in special works. This genus is the first of the sub-
family Helicinffi, in which the spiral shell is thicker and stouter than in the preceding
divisions, and capable of containing the entire animal when retracted. Most of the
species have the outer \i\> thickened and reflected, and not infrequently the aperture is
greatly reduced by tooth-like processes which
may arise from the columella or the outer li|i,
or from both. The species are usually much
larger than those in the sub-families just passed.
The characters of the genus Helix are vei'v
poorly defined, and the shape of the shell varies
between very wjde extremes. In some the
spiral is high, in others it is nearly fiat. In
most of our northern species the shell is honi-
colored without ornamentation, but in the
tropics brightly colored species are tlie rule.
The color may be laid on in blotches, or more

frequently in stripes, which follow the spiral of the shell as in the adjacent figure of
Helix si/danensis, whicli, as its name indicates, comes from Africa.

With such a wealth of species to choose from (about thirty-five hundred being
known) it is a difiicult task to select the few which our space will admit. Our most
common species is possibly Helix albolabris, which, when adult, reaches a diameter of
about one inch. In the young the outer lip is tliin and sharp ; but
when the full size has been reached, the lip becomes thickened and
reflected, or turned outwards, and covered with a white porcellanous
deposit which gives the specific name. Usually the columella is
smooth, but occasionally s]>ecimens are found in which a tooth is
developed. This species is found most abundantly in forests of hard
wood. In the southern states its place is taken by a similar liut much larger species.
Helix major.

The garden-snail of Europe, //. horte/i.'iis, has been introduced into several places
along our eastern coasts. It is very common on the islands in and near the harbor of
Salem, Mass., where, together witii Helix alternata, it lives in the long grass and among
the juniper-trees. This species has a white lip, and is usually ornamented with a vary-
ing number of reddish lines which follow the spiral of the shell. Each
of the islands mentioned has its own peculiar pattern of ornamenta-
tion, which seems to have been derived from the first animals intro-
duced. The method in which this species obtained a foothold on
these islands (several of which are small and uninhabited, and sepa-
rated by a mile or more of salt water from the shore) is even less
easily decided than in the case of the Zoitites cellaria.

Several of the European species are used as food, and one, Helix pomada, the Roman
snail, has long occupied a place in the economy of tlie Latin races. Tliis and Helix as-
persa are to-day extensively eaten by the French, and the latter species was introduced

Fig. 367. — Helix at
bolabriSy young.

Fig. .'iGS. — Hili.r
hnrtfusis, gar-
den snail.

314

LOWER IN VER TEBRA TES.

Fig. 369. — JJelU- thy-
roldes.

Fig. 371.

Fig. 37(1. — Helix
alfernata.

into Charleston, S. C, by the French inhabitants for the purposes of food. The writer
several years ago, tried the experiment of introducing it into New England; but
although the places where specimens were distributed have since
been carefully searched, none have been found. It may be that
the east winds and the cold of winter prove too much for it.
Some if not all of our American species are edible ; IT. thyroides,
when treated with vinegar, has a very peculiar but pleasant taste,
excelling, in this respect. Helix albolabris.

Another common species in the United States is Helix alter-
7iata, in wliich the outer lip is sharp and the horn-colored shell is
ornamented with blotches of dark brown. In New York and New
England it is even more common than II. albolabris, occurring not
only in the woods, but in the open fields as well, although it seems
far more dependent on moisture than some of the other species.
It is not so palatable as H. tht/roides. Allied to II. alteriiata is the
-^ ™^ pretty, but small species, H. asteHscns, in which .
Uy i^^ the whorls are ornamented by a number of trans-
verse ribs. It is only fduiid in the northern states.
- Helix asteris- Heli.v /larjui, which has a boreal distrilmtion, is
"'*' found on both continents. The shell is liigh, and

ornamented on the two lower whorls liy transverse ribs. "The body is so translucent,
that, when extended, the ganglionic centres can be plainly seen. In motion it is ex-
ceedingly graceful, at times poising its beautiful shell high above its
body, and twirling it around, not unlike a P/ii/sa, again hugging its
pretty harp close to its body ; the shell when in this last position, con-
tinually oscillates as if the animal [which is very small in proportion
to its shell] could not balance it ; it rarely ever moves in a straight
line but is always turning and 'whisking about, and this is done at

times very quickly and abruptly."

In a large number of species like Helix
sayi, dentif'era, etc., a tooth is always de-
veloped on the columella, like that occa-
sionally found in Helix albdlabris., while in
another series, including tridentata, palliata, etc., the aper-
ture is still farther contracted by the development of one or
more teeth from the inside of the outer lip. In one of this
latter grou]!, II. hirsuta, the apei-tui'C is very narrow, and the
outside of the shell is covered with numerous short, stiff
hairs.

The sjiecies of Hidimiis are largely tropical, and the ma-
jority of the three hundred and odd species come from South
America. The animal is much like that of Helix, but the
shell is longer and has but a few whorls, while the lip is
thickened, reflected, and continuous with a callus layer on
the columella. Most of the species are large, some being
among the giants of the jnilinonates, only exceeded by the
Achatince to be mentioned in a moment. The largest species is Hidimus ovatus which
is common in the forests of southeastern Brazil ; the shell reaches a length of six inches.

Fig. S'2.— Helix
harpa.

Fig. 313. — Bulimus.

0%

9C^

0

AMERICAN LAND SHELLS.

1. Helix indentata. 2. H. inoriiata. 3. H. electHna. 4. H. ferrea. 5. H. minutissima. 6. H. siip-
pressa. 7. H. ckersina. 8. H./uliginosa. 9. B". arborea. 10. H. exigua. 11. H. multidentata,
12. H. minusculus. 13. S. binneyana. 14. //". labyrlnthica. 15. ^. striatella.

MOLLUSCS.

815

Tliis species is an article of food and is sold in the markets of Rio Janeiro. Its eggs are
also very large; they have a white calcareous shell, and equal in size those of a pigeon.

Fig. 374. — Helix palUata.

Fig. 37a

-Helix saifi.

Fig. 376. — Helix dentifera.

In the older works several species of Bulimus were credited to the United States,
but more recent studies show that these forms belong elsewhere in schemes of classifi-
cation.

In some of the South Sea Islands, esjiecially in the Society group, occur a number
of land shells united under the generic name Partahi. These are brightly colored and
much like Bulimus in shape. Formerly tliey were very abundant ; but a few years ago
a great storm utterly destroyed the groves in which they were found and almost extin-
guished the genus. Unlike most of the pulmonates they bring forth their young alive,

-Achnima mauiUmn a

and the sliells are more frequently sinistral than in the other genera of the Helicidas.
In the genus Binneya occurs a peculiaiity first noticed by Dr. J. G. Cooper. The
species are all inhabitants of Mexico and Southern California. At the ai)])roach of the
dry season they retreat as ilo the IleUccs of more northern climes in the winter. Still,
as the shell is too small to contain the whole body, the epiphragm is greatly enlarged
so that it covers all the jiarts whicli would otherwise be exposed. This epiphragmal
envelope is white and parchment-like.

316

LOWER IN VEll TEBRA TES.

The sub-family Achatinin£e embraces forms much like the Heliciuoe but disting-uished
by lingual di'iititiou and by the fact that the lip is usually sharp, the columella trunca-
ted, the shell with an elongate sj^ire, tlie body whorl being swollen. The genus Acha-
tina, the agate shells, derives its name from the usually banded species. It embraces
the largest species of jiulmonates known, even exceeding the genus JiuUmus in this re-
spect, as some of the shells measure ten inches in length. The eggs are of proportion-
ate size and have a calcareous shell. Most of the sjiecies are found in Africa, where
they live in trees, descending to the ground to lay their eggs.

In the genus Achatinella, the dextral or sinistral shell is mucli like that of Btdimus
in outline, but is distinguished among other characters by the spiral fold which accom-
panies the columella. The species are confined to the Hawaian Islands, but their num-
ber has been nmltiplied to an utterly unwarranted extent, no less than three hundred
having been described. All are very pretty shells, with a polished exterior, and striped
and spotted with bright colors, red, green, and brown predominating. We well know

Fig. 37K. —Pupa
coniracta.

Fig. 379. — Pupa
armifera.

Fig. 3t.n.— Pnpa
pi'Htoilon,

Fig. 381. — /'wpa
bad'ta.

Fig. 3S2. — Pupa
fallax.

how inconstant is the number of bands in the land shells of the United States, where
the same sjiecies may be plain or ornamented with one or several spiral bauds, but
these Achatinelhi; have been divided uji mostly on similar characters. They live
largely on the low shrubbery near the sea, Ijut since the introduction of cattle on the
islands they have become much less common than formerly, on account of the destruc-
tion of their food jilauts; and their ultimate extinction is but a cjuestion of time.

In the PuPiD.E, we have a large number of generally small, many whorled, more or
less cylindrical shells, in which the aj.erture is frecpiently contracted by tooth-like
lirocesses, like those previously described in some of the Helices. Our American
species of Piqnt are almost all very minute, so that it requires good eyes to collect

Fig. 383. — Vertigo
ovata.

Fig. 3S4. — Vertir/o
viliUim.

Fig. 3S5. — Verliyo
boUesi<iviif>.

Fig. 3S6. — Vertiijn
ventrlcosa.

Fig. zm. — Vertigo
simplex.

them. They seem to be even more de|iendent <in moisture than most other land
shells. The species are lara-ely based nu the number and form of the teeth of the ajier-
ture, the variations in which may be seen in our figures of some of the more common
species from the United States. One of the most important distinctions between
Vertir/o and Pirpa lies in the fact that in the latter genus the cephalic tentacles are
present, though small, while in the former they are absent.

The srenus Clausilia occurs in the regions surrounding the Mediterranean, its

MOLLUSCS.

317

ian-
truncata.

seven hundred nominal species being distributed in Eurojie, Asia, and Africa. The
shell is long and cylindrical or fusiform, and is usually coiled from right to left, although
dextral forms occur. 'J'he animal is also sinistral, the genital and respira-
tory orifices being on the left side of the body. The aperture is usually
distinct from the rest of the shell, being separated by a neck or constric-
tion. We have already alluded to the peculiar permanent epiphragm
'.vith which these forms close the aperture.

The members of tiie family Suci-inid.e have a world-wide distribu-
tion, and are usually found near the margins of ponds and streams. The
shell much resembles that of tlie Limneans, though the two families are
widely different. The family is distinguished from all others by the
upper jaw, which consists of the usual arcuate portion backed up by a
quadrate plate. The shell is very tliin and trans])arent, and made ui> of
a few rapidly enlarging whorls. The principal genus is Succineu, of ^sJ/jff^(^™cai
which about two hundred species are known. These forms have an

oval aperture and a sharp outer lip, and are usually
regarded as amphibious or even as preferring a sub-
aquatic life. This belief does not apjjear to be well
founded, for, although they are found near the mar-
gins of streams, they live exclusively in the air,
and some of them are found far from any body of
water.

At the time of drought, and at the approach of winter, tliey draw the body com-
pletely within the shell, and form an ejiiphragm like that of the Helices. The shell
is amber-colored or whitish. Our most common species are Succinea auara, and S.
ohliqua.

Tlie terrestrial pulmonates in which the shell is internal or absent are known in
popular parlance as slugs, while in scientific works they are united into a family to
which the name Limacid^ is applied. Their general appearance is too well known to

Fig. 389, — a, Succinea totteniana; b, S.
ovalis ; c, S. avara.

Fig. 390. — Llmax maxlmus.

call for any detailed description, yet there are certain features whicii have a morpho-
logical significance to be mentioned. On the dorsal surface of the bod}-, near the
anterior end, is a fleshy plate, the mantle. At or near the right margin of this,
is the opening of the respiratory pore. The iiead is well defined and provided with
tentacles.

The slugs are chiefly nocturnal, and this fact accounts for the few ordinarily seen,
although tliere may be thousands about. In the daytime they secrete themselves
under boards, fallen trees, etc., where there is at least partial darkness, but at night
they come out to feed. They do a great amount of damage in gardens, as they feed

318 LOWER INVERTEBRATES.

largely on vegetation, although they are not averse to an animal diet. Since they
hide themselves dm-ing the day, the damage tiiey occasion is usually attributed to birds,
and the larvae of insects, but the presence of slugs can usually be recognized by the pres-
ence of streaks of glistening slime in the neighborhood. Most of the terrestrial jnilmon-
ates are able to secrete a mucus from their body, and in some there are sjieeial jiores
for its emission. In the slugs this capacity reaches a great development, and as they
crawl along they leave a streak behind them, which, on drying, produces the glistening
marks referred to. This secretion of mucus is to a certain extent defensive, and
when the animals are irritated the amount is greatly increased. This fact gives us a
simple method of checking their ravages, which is to sprinkle coal-ashes around the
plants which it is desired to jjrotect. The fine grit of the ashes irritates them, and they
pour out the mucus to such an extent that they are soon exhausted, and besides, since
it rapidly hardens on exposure to the air, they are soon rendered prisoners.

This secretion of mucus is used in another way. Slugs frequently climb trees in
search of fruit, and when through feeding they take a quicker method of descending
than their ordinary snail's pace. The foot poui-s out a lot of mucus, which is passed
along to the posterior end. This mucus is then attached to the limb on which the
animal is, and then the slug casts itself loose. Its weight draws the mucus out into a
tine thread, .and, more being secreted, the slug lets itself down after the fashion of a
spider, with this exception ; it has not the power of returning to the point of support.
This power of forming a thread has been observed in almost .all the American species,
at least when young ; but some of the larger forms, when adult, fire too heavy to trust
their weight to such a slender support.

We have spoken of their rav.iges in gardens, but in America they have not yet
become such a pest as in Europe. There they are classed along with caterpillars,
locusts, and rats, and a war of extermination is waged against them. In olden times the
power of the church was invoked against them, but prayers and anathemas failed to
cause their extinction, or in fact any .appreciable diminution of their mnnbers. There
is another aspect which should not be passed by without mention. Slugs have long
been supposed to have medicinal ipialities, the rudimentary shell being regarded as
especially efficacious. This belief can hardly be regarded as extinct, as Mr. Binney
s.ays that " during the year 1863, a syrup of snails was prescribed to members of my
family, by two regular French physicians in Paris." During the middle ages, when
superstition ran riot, of course they were much more highly esteemed. The shell was
regarded as an amulet, protecting the wearer against certain diseases and witchcraft,
while the liquid obtained by their distillation was used to imjjrove the comjilexion.
In Europe they are eaten, but in America neither dietetic nor magic qualities have
been assigned to these loathsome appearing animals.

The Limacidse .are divisible into three su])-families. In the first, the Tebenophori-
nse, the mantle covers the entire back, and no shell is present. Our only species is
Tebenophoms carolinensis, a sluggish, inactive form found in the woods, usually under
the bark, or in the interior of decaying logs. It varies considerably in color, from
nearly white without spots to white with brown blotches or black spots, and to black-
ish gray. It reaches a length of about four inches \\'hen fully extended, though at
such times the head is not projected beyond the Tnantle.

In the Arioninse the shell may be present, though concealed by the mantle, oi- it
may be represented by a number of calcareous grains scattered through the corre-
sponding portion of the mantle, a condition which recalls the embryonic condition of

MOLLUSCS. 319

Limax, as shown in Fig. 348 on a preceding page. In the princijial genus, Arion,
there is a triangular pore at the upper posterior part of the body, which readily sep-
arates it from Umax. The only spe-
cies in the United States wliich un-
doubtedly belongs to this genus is
Avion fuscus, which has been intro-
duced from Europe into Boston, where

a colony has existed for many years. Fig. 391. — .J/ , , .,

It lives in gardens, and occasionally

strays into cellars and other dark places. It is not known elsewhere in America.
In Europe it is a common species, and its eggs are said to be phosphorescent, shining
in the dark for several days after being laid. In color this species is whitish or gray-
ish, sometimes tinged with brown. It i-eaches a length of about two inches.

Three other genera of Arioninse, Arioliniax, Projyhysaon, and Hemphtllia, are
found on the Pacific coast.

The' last sub-family, the Limaciiue, embraces the largest ])roportion of the slugs,
the typical genus, Limax, containing about one hundred species. This is the only
genus represented in the United States, where, besides our native species, we have
se\'eral introduced from Euroi>e. Our largest species, Lirnax inaximus, is one of these
immigrants, which has been found in several places hi America. Its rich brown or
black spots and stripes upon an ashy or light brown groundwoi'k make it a conspicuous
form.

Another imjiorted species is i. ,/f(;i'MS, brown or brownish in color, with lighter
spots. This is more eomnidii tlian L. maxhnics, and is found in various Atlantic cities

from Boston to Charleston. It lives in cel-
lars and in gardens, preferring the former.
Still more common is the smaller X. agres-
tis, which is also an introduced form. It
is smaller than the others, and is extremely
\'ariable in color. It lays more eggs than
the two species mentioned, and the period
of reproduction a])pears to last through the
warmer months of the year. Our native Lirnax carnpeatris is very common, and is
found in the woods and the open fields, along the sides of the roads and in gardens.
It is brownish gray or amber colored, and is smaller than the other species men-
tioned. The eggs are rather numerous and transparent, and are laid under leaves or
in moist earth. Di-. E. L. Mark has studied the earlier stages of the development of
this species ; a later stage is shown in Fi^■. 348.

Another genus, Phosphorax, which is very imperfectly known, comes from the
Cape Verdes. The only species is said to be phosphorescent, as is indicated by both
its generic and specific names (P. noctihi.cens).

Order III. — ZYGOBRANCHIA.

All of the gasteropods which follow Ijelong to the Stre]itoiieurous group, the
characters of which were detailed on a jjreceding page. In the first division, the
Zygobranchia, the torsion of the body has not been accompanied by an atrojihy or
disappearance of the organs of the primitive left side, and we thus have the gills and

320

LOWER INVERTEBRATES.

Fig. 393. — Baliotis, abaloue.

openings of the renal glands of both sides reniainhig, thus showing that the group is
more primitive than those which follow it. Another fact that also emphasizes this
inferiority is the absence of distinct genital ducts, the products of the reproductive
organs escaping by the larger renal opening. The lingual ribbon is well developed.

The faniilj- Haliotid.e embraces the forms which are familiarly known as ear-
shells, and to which the local terms ormer and abalone are applied in the Channel

Islands and soutliern California respectively. The shell is
sph-al, the body whorl being flattened and very large. The
dorsal surface of the shell is perforated by a line of ojjenings
through which pass a series of tentacular processes from the
*>0^'- - /' '^ JBIf mantle. As growth proceeds, these are closed up posteriorly.

The eyes are on short stalks. The forms are mostly tropical
and semi-tropical in their distribution, and are extensively
collected for their beautiful shells, which are an article of commerce. The shells
furnish a large proportion of the mother-of-pearl, especially that used in inlaying
ixipier maclie ornaments. In France and the Channel Islands, ormers are used as an
article of food, but on account of their toughness they require pounding and mashing
before cooking.

The FissuKELLiDJE, or key-hole limjjets, are structurally closely allied to the last
family, but in external appearance they seem far different. Tlie shell
is conical and shows but very slightly any spiral. Tlie series of open-
ings of the Ilaliotis are replaced by a hole at or near the apex of the
shell, or by a notch in the front margin. On the inside of the shell
is a horseshoe-shaped impression, indicating the surface of attach-
ment of tlie muscles of the foot. The eyes, instead of being placed
on stalks, are scarcely elevated above the surrounding surface. Like

the members of the last family,
the sj)ecies are largely inhabi-
tants of the warmer seas of the
globe, although some forms are boreal in their
range. They are mostly found near the shores,
where they feed upon the smaller seaweeds. In
their habits they are not different from the other
limpets.

The third family of the Zygoliranchia, the
PATELLiDiE, is appai'ently far different from
the other two in the structure of the gills, and
the fact that it really sliould have a place here
is shown by one of the neatest bits of morpho-
logical logic w'ith which we are acquainted. On
tlie first examination of a Patella we find a res-
jiiratory organ in the form of a circle just be-
neath the mantle, while the branchise above the
neck, comparable to those of Ilaliotis and Fis-
sweNa, are absent. S]iengel, however, found
in this region two little jirominences, the ho-
mologies and functions of which wei'e obscure. The thought, however, suggested itself
that these might be the rudiments of the true gills and an anatomical examination

v^iKr-

Fig. 394. — Mssur-
ella nodosa, key-
hole limpet.

Fig. 395. — Under surface of Patella ataira ;
foot; b, edge of mantle; c, gill; d, liead;
tentacles.

MOLLUSCS.

321

showed that this view of the homology was correct. It will be remembered that the
typical gill is innervated from the visceral loop of the nervous system, and that near
its base is a patch of olfactory e]iith^4iam (see p. 25Uj. Dissection of a Patella showed
that these jjrominences received their nerve supj^ly from tlie \isceral loop, and near
each was found an olfactory organ, thus making the homology complete and indisiDut-
able. The circular functional gill is therefore a superadded structure which has arisen
in a manner and from some cause not yet explained.

Not all limpets have been shown to belong in this place, although future in-
vestigation may demonstrate that they should be classed here, a view which is
strengthened by the similarity in lingual dentition. Still, for
convenience, it will be well to consider the Acm^id^ together
with this family, as in general appearance and in many important
points of structure they are closely similar. In these forms there
is a single cervical gill, while the circular marginal gill may be
either present or absent. The prominent genera are Acmcea,
Lottui, and Scnrria. In Lepeta no gills are found.

The shell in the limpets is conical, usually considerably de-
pressed, and is so characteristic as to have given rise to the adjec-
tives patelliform and limpet-like. The apex jioints forward, and
tlie internal horseslioe-sliaped muscular impression, like that of the
Fissurellida', is open in front. A large number of genera and
sub-o'enera have been made, the characters restins' ui>on the res- ^"^- stiG. — .-jrmffa tes-

^ ^ i tudmalis^ limpet.

pu'atory organs, shape and ornamentation of the shell, etc.

As ordinarily found, the limpets are attached to some rock or other object by their
broad foot, and the strength with which they hold is astonishing. If the collector ap-
proach tlie animals suddenly, and with a quick motion slides them from their attach-
ment, he can get them easily, but if an incautious touch gives them warning of danger,
the shell will not infrequently break before the animal loosens its hold. The strange
story is told that each limpet has its own abiding place. At the time of high tide he
wanders off to find pastures of alga3 suitable for his palate, but as it ebbs he returns to
his chosen spot, and at low tide clings fast to the same spot on the rock which he left
a few hours before.

On the European shores, limpets play an important part in the diet of the people
living near the shores, but on our coasts, except a very few used as bait, they have no
economic importance. Why it is that our people neglect so many articles of food it is
impossible to say. In the northern states, shrinijis, limjiets, periwinkles, mussels, etc.,
are scarcely touched ; yet the sea teems with thein, and everyone who has tried them
bears witness to tlieir palatability. In the case of the limpets it may be that the com-
parative scarcity on our coasts may be tlie cause of their neolect.

Acmaa testudmalis, the most common limjiet on our nortliern coasts,

belongs to the family AcmteidiE mentioned above. Its position here is

extremely doubtful, and aside from the fact that its branchial system has

never been studied, our only excuse for mentioning it liere is to treat of

all the limpets together. This species is very varialile in color, but is

^'°' a^fc^M.'""^" usually variously mottled with brown, pale green, and white. Like most

of the limpets it lives between tide-marks. Aemrea aluens is a variety of

the foregoing, liut, from the habit that it has of living on eel-grass, it has acquired a

narrower shell than the typical form.

VOL. I. — 21

322

LOWER INVERTEBRATES.

Order IV. — SCUTIBRANCHIA.

All the remaining Gasteropoda contrast with the Zygobranchiata in the fact that
the torsion of the body has caused the obsolescence or abortion of one of the true gills,
and for this reason Dr. Lankester has arranged them under one ordinal head Azygo-
branchia. Wlien, however, we take other characters into consideration, it becomes
necessary to divide up this large group, and in the following pages the Scutibranchia,
Ctenobrauchia, and Heteropoda together equal the Azygobranchia of that able Eng-
lish morphologist.

The first family, the Teochidjs, are commonly known as top-shells, the shell of the
typical forms, when inverted, being sti'ikingly similar to the j^laything of our youth.

Tlie shell is sjjiral, and is either pyra-
midal or turbinated, and has a nacreous
interior. Many of these shells are sold
as ornaments, after the epidermis and
external layers of the shell have been
cut away, leaving the whole a mass of
mother-of-jiearl. The animal has long
and slendei- tentacles, .'uid at the bases
of these ai-ise the peduncles which sup-
port the eyes. The head, and sides of
the l>ody, are ornamented w ith fringed
lobes and longer tentacles. When the
animal withdraws into its shell, it closes
the ajierture with an operculum, which
may be either horny, or calcareous with a liorny base. As the .animal increases in size,
the operculum also grows by additions which are .arranged in a spiral. When crawling
about, the animal carries its operculum on the dorsal surface of the foot, as do all oper-
culated gasteropods. Some of the ojierculaof the smaller species are in great repute
as eye-stones. Their whole value in this respect is due to the fact that they have no
irregularities which would injure the cornea or the inner surf.ace of the eyelid. Otlier-
wise they are no better than .any other hard substance of similar shape and size. The
physiology of their action is readily understood. The
species live in sh.allow water ne.ar the shore and are
herbivorous in their diet.

In Trochi/,.% the shell forms a regular pyramid, and
the base is flattened. The whorls are flattened, the aper-
ture is oblique, and the operculum is horny and multi-
spiral. Of this genus and its various sub-di\isions, over
two hundred and fifty species have been described. In

our northern waters, these forms are represented by several species of

the genus Jlarf/arita, which in many respects is intermediate between

Fig. 4(10. — .i/ar- Trochus and Turbo. The whorls of the shell .are more ventricose, or

'""'"' swollen, than in Trochus, and the thin e]iidermis allows the pearly shell

to be readily seen. The species are found from extreme low-water mark to a depth of

one hundred fathoms and over.

In Turbo the whorls are ventricose, the aperture large and rounded, and the

Fig. 398. — Delphiiiula lacinluta.

Fig. o'M.— Trochus zlzijplmms.

MOLLUSCS.

323

Fig. 401. — Turbo marmoratus.

operculum calcareous ; the base of the shell is never flattened. The species are
mostly trojiical and littoral, delighting in rocky coasts where they are exposed to the
force of the waves. In the Orient the larger species
are eaten. The largest species known is Turbo mar-
moratus of tlie Chinese Seas. In Delphiimla the shell
is depressed, the aperture round and pearly, the um-
bilicus open, the operculum horny, and the whorls of
the shell are usually s|jiuy. The genus is found on the
coral reefs of the ludo-Pacitic Seas, near low-water
mark. Our figure shows the under surface of the shell,
with the body extended.

Phasianella contains species which have somewhat
the shape of the genus Sulunns among the pulmonates.
The shell is not pearly but is richly colored ; whence
the name pheasant shells. About forty sjaecies are
known, all from tropical seas. Those from Australian and New Zealand seas are large,
reaching occasionally a length of about two inches, but those from other parts of the
world are smaller, our West Indian forms being very small. Rotella contains a number
of brightly-colored dejiressed species from the eastern seas. In 3Ionodoitta, which is
much like Turbo in general appearance, the outer lip is much thickened and grooved,
while tlie columella is toothed. It has about the same distribution as the last species.
In the Malay Archipelago one of the species is eaten, notwithstanding its peppery
taste.

The Neeitid^e contains thick hemispherical shells with a very small spire, a sharp
outer lip and a calcareous operculum which is frequently irreg-
ular in shape. The eyes are placed at the extremity of the
slender eye-stalks, which arise from the head outside the long
and slender tentacles. The foot is broad and triangular, the
apex being behind. As the animal grows, it absorl)S the inner
])art of the whorls of the shell, so that the resulting cavity is
simjjle instead of spiral. The tyi>ieal genus is JVerita, which
has a thick or spirally grooved shell. The columella is much
thickened and toothed, and in one species, N. peloronta, this
coluraellar thickening is ornamented with a blotch of red, giving the shell the common
name of bleeding tooth. Most of the species are marine, but many ascend the streams
entering the ocean to such a distance that the water in which they live is brackish.

Neritina is much like JSferita, but is more glolmlar. The shells are variously orna-
mented with spots or bauds of black and purple laid upon the polished extei-ioi-. The
sjiecies are mostly confined to the fresh waters of the warmer regions of the earth,
but some species are found in the sea. Namcellu is more like the slipper limj^ets
{Crepidula) in appearance, the aperture embracing nearly the entire shell. They ai-e
fresh-water forms, and the resemblance to the limpets is strengthened by their mode
of life as they attach themselves by their foot to submerged stones and plants.

The family Pleueotomarid^ shows resemblances to both the Troehidse and tlie
Hahotidae. The shell is much like that found in the l.-itter family, exeejit that the outer
hp of the aperture is notched, or there is a series of perforations in the u]iper part of
the whorl. The species are largely fossil, the living forms being few in number and
comparatively rare. In most of the species the notch in the aperture of the shell is

Fig. 402. — Xerita histrlo.

324 LOWER INVERTEBRATES.

closed behind as grouth progresses, and tlie result is that each whorl receives a band,
which is quite distinct from the rest of the shell. In some of the fossil sj)ecies this is
very marked, and stands up elevated to a considerable distance beyond the sur-
rounding surface ; in others the closing up is not complete, and the result is that there
remains a series of holes like those of the abalone (Ilaliotis). Recent deep-sea ex-
plorations have largely increased the number of known species of this family, most of
which are apparently inhabitants of water from four liundred to a thousand fathoms
in depth.

The IIelicinid^e is a family of terrestrial gasteropods variously placed by different
naturalists. Most commonly the members are placed among the true land shells (pul-
monates), but with these they have little or no affinity. We follow
Claus in assigning them their present position. In apjiearance of
tlie shell, in the structure of the lingual riljbon, as well as in their
haljits, they are much like J/eli.c, living as they do ujion the land,
either concealed under the dead leaves on the ground, or among the
^"'' mrira^a ''^""' branches or foliage of the trees. They differ however, from the
Helicidie, among other important points, in the possession of an oper-
culum. The aperture of the shell is semilunar, and the umliilicus is covered by a
callus. The species are all tropical, and are mostly confined to the Ameiican con-
tinent and the West India Islands. Only a few species out of the five hundred
known are found within the limits of the United States. The prominent genera are
Selicina, Stoastonia, and Proserpina.

Oeder V. — CTENOBRANCHIA.

Most of the members of this group despise a vegetable diet and prefer to live on
animal matter whether living or dead. Still, some exceptions occur which will be no-
ticed in the proper places. In all, the shell is spiral, and the gill of the normally right
side is alone present. What has previously been considered as the rudimentary gill of
the left side has been shown by Spengel to be tiie highly developed olfactory organ.
The gills lla^■e a comb-like shape and the axis is frequently attached to the roof
of the branchial chamber, which by that torsion of the body described on a preceding
page, is brought above the neck of the animal. In many, a well-developed co]nilatory
organ is found on the right side of the neck, and the proboscis may or may not be re-
tractile. The former condition of affairs lias given rise to a group called Proboscidi-
fera, containing the families Tritonidas, Doliidie, and part of the Muricidse as here lim-
ited, while another group, containing the Cyprajida;, Yelutinid.a?, and Naticidie, have
the rostrum invertible only at the tip.

The Ctenobranchia is divided into four sub-orders„the distinctions being largely
founded upon the arrangement of the teeth upon the lingual ribbon, although other
characters are of course employed.

Sub-Order I. — Ptenoglossa.

In this group the shell has the aperture entire ; that is, the whorls are complete and
the edges of the aperture are not notched or prolonged into canals. No res))iratory
siphon is formed, and copulatory organs are absent. The tongue is armed with numer-
ous small teeth on either side, but lacks the normal middle row.

MOLL uses.

325

The Iajtthimtd^ are remarkable for the beautiful purple color of their tliin shells.
They are 2:)elagic, oceanic snails, which lead a predaceous life. At times ou the high seas
the navigator encounters vast numbers of them, forming immense schools, and feeding
upon the other forms of life ; medusffi, Crustacea, etc., with which they are surrounded.
The animal has a large head furnished with an extensible proboscis. The eyes are
minute and situated on the extremities of the ocular peduncles, while the foot is small
and divided. The shells are tliin and delicate, the whorls of the spiral being few in
number. At the base they are of a deejj violet color, but the apex is nearly or entirely
white.

One of the most interesting features connected with these shells is the enormous
float which they form to support the eggs. The foot secretes a glutinous secretion
which hardens to a slight extent when brought in contact with the water. During the
reproductive season the formation of this egg float is continuous, and, as it is formed,
eggs are fastened to its lower surface. From this mode of formation, that part of the
float farthest from the animal contains the most advanced eggs ; and, in fact, the eggs
in this portion may have hatched and the embryos have begun their free life ere those

Fi<;. 404. — lauthina, purple shell, ^vith the float supporting the eggs.

nearest the body have passed through the enrliei' stages of development. Although
the parent usually carries the float attached to the body, still it has apj)arently the
power to cast it off at will, while the action of storms usually separates the mother
from the egg. When thus cast adrift, the float still sustains the eggs, and they pursue
their development as usual. Each egg is fastened to the float by a short ]ieduncle,
while the float itself is composed of numerous little bubbles, thus securing great
buoyant powers.

The lant/iince do not appear to have the jiowerof sinking in the water unless the
float is detached, and so at the time of storms they are frequently cast ujjon the shores
in large numbers. At such times they are utterly helpless and make no attempts to
crawl. They, however, frequently adhere to each other by means of the foot, and,
when handled, secrete a violet-colored fluid.

laiit/iina, the most prominent genus, contains about ten sjiecies, one of which (T.
fragilis) is occasionally thrown up on the southern New England coasts by severe
southeast storms. It is not jiroperly a member of the American fauna, liut like tlie
rest of the genus is an inhabitant of the high seas. The only other living genus of
the family (Heclmia) is covered with a brownish ejiidermis. Like Jant/ii/xi, it forms
a float.

The SoLARiD^aj embraces a group of molluscs which, from the shape of the shell,
was formerly included in the Trochida). The shell is orbicular and forms a more or

326 LOWER INVERTEBRATES.

less flattened cone, usually perforated by a wide and deep umbilicus. The shells are
not nacreous, and a horny spiral operculum closes the usually angular aperture. The
animal has sessile eyes, long, retractile proboscis, and the gill chamber divided into
two parts.

^Solarium 2}erspectwwn has received tlie common names of perspective shell and
sun-dial shell. It is about two and a half inches in diameter, and is of a yellowish
hue, prettily spotted and banded with red. It comes from the Indian Ocean, and
specimens are found in most collections.

The only other genus which needs to be mentioned is Phoriis, which embraces the
carrier or mason-shells of the eastern seas. These forms have the habit (if habit it
may be called) of covering their shells with all sorts of extraneous objects, — shells,
stones, bits of coral, and the like. These foreign bodies are fastened by the substance
of the sliell and doubtless are protective ; for, viewed from above, a shell thus tricked
out has but slight resemblance to a properly conducted mollusc, and thus runs a better
chance of escaping the maw of the bottom-feeding fishes. Now that this peculiar
habit exists, we can readily see how it is retained, but the way in which it was first
acquired is not so readily explained.

The mode of progression of the mason shells is rather peculiar. Most of the gas-
teropodous molluscs have a gliding motion, the various parts of the foot acting in a
manner best described by comparing it to the locomotion of a thousand-legged Morni.
The Phori., on the other hand, have a g.ait like that of a measuring worm. They
extend the small cylindrical foot, attach the anterior portion, and then draw the hind
portion forward. This latter now affords a footliold; the anterior portion is again
extended, and the operation is repeated. This gives rise to an interrupted, almost
jumping movement, well adapted to the banks of broken coral and dead shells inhabited
by these animals.

The Sc'ALARiD^, or wentle-traji family, embraces but a single genus and about a
hundred and fifty species, distributed through all the seas of the world. The common
name is a corrui)tion of the German word for a spiral stairway, and would be emi-
nently appropriate, were it not for the fact that tlie tread of the stairs goes the wrong-
way. The shells are usually pure white, and comjiosed of several rounded whorls
ornamented with transverse ribs, roughly corresponding to the stejjs of a fliglit of
stairs. The aperture of the shell is round and the edge continuous, the inner lip not
being formed by the coluinella. The active, predaceous animal has
a retractile proboscis, and in the existence of a rudimentary siphonal
fold shows an approach to the members of the next sub-order. The
eyes are near the outer bases of the slender, pointed tentacles.
Sever.al species of Scalaria are found on our New England coasts.
Mr. Couthouy kept a s]iecimen of S. gronlandica in confinement;
it was rather sluggish in its movements, and fed eagerly on fresh
beef, especially if somewhat macerated. Some of the species are
said to secrete a purple fluid.

The most noted member of the family is Scalaria ]wetiosa,
FiG.405.-Sca!ariaprc- t'lP prccious wcutle trap. This species, which comes from the
tjosd, precious wen- Chinese Seas, has always been hiarhly valued by collectors on

tle-tr,ap. ' ■ o ./

account of its rarity, and a smgle specmien lias m tunes ]>ast been
sold for about two hundred dollars. Now they are much more common, and are sold
by dealers for an average price of one or two dollars.

MOLLUSCS.

327

Sub-Okder II. — Rhachiglossa.

The Rliaelii<i-lossa are all preilaceous marine snails with well-developed proboscis
and a respiratory siphon, which, when the animal is extended, lies in a notch in the
aperture or in a long, more or less tubular canal of the shell. The tongue is long and
small, and bears at the most but three teeth in a transverse row, one rhachidian and
one lateral on either side, the latter being occasionally reduced to mere hooks, or, as
in the case of the Volutidse, they have entirely disappeared, and the central or rhachi-
dian teeth alone remain. All are predacious and carnivorous.

We have iust referred to one of the characters of the Volutid.e, but now we
may give some others derived from other parts. The shell is thick and heavy, and
the spire is short, rising but little above the body
whorl. The anterior margin or base of the aper-
ture is deeply notched for the respiratory siphon,
while the columella bears strong spiral plaits or
folds. The eyes are placed at the base of tlie
tentacles, and the foot is large and broad. The
typical genus is J^oluta, in which the spire is
short, the mouth wide, and the first fold on the
columella is the largest. The species are largely
from the Indo-Pacific region, although some are
found in other seas. One of the most interesting-
species is that figured. It derives its s]>ecific
name, miisica., from a number of fine dark lines
interspersed with blotches, whii'h follow the
whorls of the shell and bear no distant resem-
blance to written music. In some the similarity
is more marked than in the specimen figured.
This species presents an exception to most of
the Volutes, in having a small operculum de-
veloped. It comes from the West Indies.

As an example of the forms from the eastern seas we may mention the beautifully
shaped species from the Philippine Islands, which, from its diadem of spines and its
size, well deserves the name, Voluta imperialis, which science has gi\-en it. It is
common in collections. The last species which we can mention is the rare Voluta
junonia, or, as it is called by dealers, the peacock-tail volute. The figure i-epresents
the shell of the natural size ; it is white, sjiotted with orange. For many years it was
considered among the rarest of shells, specimens having been sold for about two
hundred dollars, and no later than 1876 a specimen brought fifty dollars. Recently
quite a number have been brought from the West Indies, and now they can be bought
of the dealers for eight or ten dollars.

Most of the Volutidse are ovo-viviparous ; that is, they bring forth living young:
but some, if not all, of the genus Voluta lay eggs, which are envelojied in a ]icrfectly
transparent, corneous corpuscle half as large as the parent. Cymhium and Melo bring
forth their young alive, a brood containing four or more individuals.

In 3IargineUa we have some two hundred species of small, polished oval shells
with the respiratory notch small. Most of them are brightly colored, and in life the

Fig. 40G. — Voluta musica.

328

L 0 WER INVER TEDRA TES.

markings of the body are even more beautiful tlian those of the shell, as is shown by
the following description of the colors of a Javanese species, — "a pale, semi-transpa-
rent, pinkish-yellow mantle, with a range of semi-elliptic crimson spots around the

Fig. 407

- Voluta junmiia.

Fig. iOS. — Vuliita iiiqitrUdis.

thin free edge, and the remainder covered with vertically-radiating linear spots,
and short waved lines of the same color; the foot, also of a yellowish, delicate
jiink, is marbled all over with the dee])est and richest crimson, and the same with
the siphon. The tentacles are yellowish, with a row of marbled crimson spots."
Sjiecies of Marginella are found in all the wanner seas of the world, some being
found in the West Indies and on the coasts of Georgia and Florida.

The (ilivc shells, belonging
to the family Olivid^, have
always been favorites with
collectors on account of the
beauty of their smooth and
jiolishcd porcellanous shells.
In these forms the sjiire is
i short, the ajierturc deejily
jiotched, the columellar lip is
covered with a callous dejiosit
and usually ornamented with
; oblique folds. In the genus
Oliva, which receives its
name from a shape somewhat
like that of an olive, the ajierture is long and narrow, and the columellar lip is plicate.
The foot is very large and is laterally extended into two lobes, which, when the animal

MOLLUSCS.

329

is in motion, are folded up over the shell. The proboscis is short, the siphon long, find
the eyes are placed at about the middle of the tentacles. The eighty and odd known
species all come from the tro]iics, a few only extending their range outside. They are
all active, predaceous forms, and in some localities are caught by lower-
ing a net with a piece of meat inside as a bait. In some ]>laces the num-
ber of specimens is almost infinite; at low tide miles and miles of ilats
are covered with them.

One of the most common species in collections is a little whitt form
belonging to the sub-genus Olivella ; from its resemblance to a grain of
rice it has received the specific name oryza. It comes from the West
Indies, in some parts of which it occurs in vast numbers. The sub-
genus Olivella is distinguished from Olioa proper by the longer spire
of the shell and the absence of tentacles and eyes. Olivella biplicata, oeiiu bipUcata.
which is figured, comes from the Pacific coast.

Of the tru? Olivas, the most common species in the southern United States is
0. litterata, marked with angular markings, which by a stretch of the
imagination might be regarded as resembling writing. The general
color is a yellowish white, the markings brownish. Another lot of
shells are named, from their resemblance to certain rocks, jas^ndea,
porphyria, etc. The latter species comes from Panama.

The harp-shells (genus Ilarjnt) differ markedly from the other
mendjers of the family by their broad aperture, and swollen, trans-
verseh'-rilibed wluirls. Although only nine species are known, every
collection contains several specimens, those of Ilarpa veiitricosa being
possibly the most common. Large as is the shell, it is not sufficient
to contain the whole animal, and Semper, as well as the older natur-
alists, record a peculiar habit of self-mutilation with some of the spe-
cies from the eastern seas. When cajitured, a part of the foot
remains outside of the shell. This the animal brings across the sharp
edge of the aperture, thus cutting it off. In time a new ]iortion grows out, reiilacing
that which was amputated. The animals are lively, and bright colored. They are
found in all the tropical seas, except the Atlantic. Ilarpa ventricosa comes from the
East Indies, //. imperialis from Bourbon, while H. creiiata and // scriba ai'e found
at Panama.

In the ]\IiTi!iD.K but a single genus, J\fitra, needs mention. Here the shell is thick,
long, and fusiform, tlie spire being well developed and the columella plicate ; the
aperture is narrt)w, notched anteriorly, and in some species is jiartly closed by a small
horny opercnluin. Mitra ejyiscopalis, possiblv the most common member of the genus,
is ornamented with spots (usually ([uadraugular in outline) of red, salmon, or orange.
It comes from the Philippine Islands, where it moves rather sluggishly over the flats,
especially when the tide has just liegun to come in. When the tide recedes, it buries
itself just beneath the surface. Some of the smaller species are more lively, and others
crawl about on the surface of the sand when the tide is out. Although frequently
seen in the day-time, the Mitras are essentially nocturnal, and spend most of the hours
of dayliglit hidden under rocks and in holes in the coral reefs. Some species, when
irritated, defend themselves by secreting a purjile fluid, the odor of wiiich is said to be
very nauseating.

Another eastern species, nearly or quite as common as the one mentioned, is M.

Fig. -ill. — Oliva
porphyria.

330

LO WE It IX VER TEBRA TES.

papaiis, which has each whorl of the s|)ire crowned with knobs, and the small colored
spots of the shell much more irregular in shajje and distribution than in JI. ejnscopalis.
The genus Mitra contains over two hundred species, a large proportion of which come
from tlie Philippines and the neighboring seas. Almost all of the genus are tropical
and semitropical ; several being found in the West Indies ; but an exception to this
distribution is found in Jf. gronlandica, as its name indicates, an Arctic form, which,
on account of j)eculiarities of its lingual dentition, has been separated as a sub-genus
^^olutomilra.

The family MuRTCiDyB, as at jiresent limited, embraces a heterogeneous assemblage
of forms. Several attem])ts have been made to divide it without doing violence to
the affinities of one or more genera, but no scheme has as yet received universal accep-
tance. If we base the division on the lingual dentition, it does not agree with char-
acters derived from tiie animal and from the shell ; if on the anatomy of the animals,
still other features are not in accord, etc. With this uncertainty it is l)est, at least in a
popular work, to leave the classitication in its present condition, and to define the
family as embracing a grouj) of molluscs, in which the foot is broad and of moderate
length, the siphon long, the eyes at the base of the tentacles, while the characters derived
from the shell are the presence of a long or short, straight, anterior canal, and an oval
operculum with the nucleus at the smaller end. Necessarily where so much con-
fusion exists there will be an inequality in the relative rank of certain of the included
tvpes, and in the following remarks some genera named will }»ossibly not be worthy of
generic rank, while others, on the other hand, may deserve to be I'egarded as really
of the grade of sub-families. The same trouble also occurs with the next family, the
Buccinidie.

The first sul>faniily, the Muricina?, is well marked by characters derived from the
shell. Tlie growth is apparently marked by periods of rest, and at each of these the
aperture is thickened and marked by ornamentations of various kinds. Then the shell
grows again, and shortly another period of rest ensues, when the nodes, spines, or
thickenings (varices they are called) of the mouth are repeated. These interruptions
occur at ^'arying intervals in different species, and are of some use in defining

generic limits. A similar process occurs in some
other families.

The typical genus is Mnre,i:, in which the canal
is long and straight, the aperture round, and the
shell is interrupted by varices and spines at least
three times in the course of the gi'owth of the whorl.
In the colder watei's the colors are subdued, and the
shell does not acquire that fantastic form that is fre-
quent in the tropical species. The species are among
the most rapacious of molluscs, boi-ing through the
shells of other s])ecies in the same way as does the
Natica, to be described on a subsequent page. In
Europe, Murex erinaceus does great damage to the
oyster beds. Allied species {M. hramhiris and M.
trrmcidus) were employed by the ancient inhabitants
of Syria and Greece in the pre})aration of the cele-
brated Tyrian purple. Of the two hundred and odd s]>ecies of this genus, we need
only mention, in addition to those just referred to, the Murex ten)cisj?ina, in which the

Fig. il2. — Murex endit'a.

MOLLUSCS. 331

canal is very long and almost converted into a closed tube, while the surface of the
shell is armed with very long and slender spines, evidently defensive in their nature.
In forms lilve 31. endiva and 31. scorpio, tlie spines are stouter and broadened at the
extremity. None of the species of J/iire,:: proper extend into the colder waters of our
Atlantic coast; indeed the genus belongs largely to the tropical w.aters of the old
world. In their place are found a few small species belonging to allied genera, of
which E'lqjieuru cauduta may be mentioned first. In this species but two prominent
varices are formed to a whorl, giving the shell a flattened aj)pearance, a fact which led
to its original description under the generic name Manella. The aperture is toothed
within, and smaller ridges occur between the well-marked varices. The shell is brown
in color, and reaches a length of about an inch. It is rather uncommon on the
southern shores of Xew Englaml, excejit in certain localities, but farther south it is
very abundant.

Urosalpin.e cinerea, on oui' coasts, jjlays the same destructive part that Afurex bran-
daris does in Euroj^e. The fishei-men have applied to it the name ' drill,' on account of
its settling down on oysters and boring a hole through the shell, through
which the soft parts are eaten. The drill is sluggish in its motions. It
is about the size of the last species, ashy or brownish in color, and orna-
mented with ten or twelve undulations on the lower whorl. It lays its
eggs in capsules, of about the same size as those of Purpura lapiUus, to
be described in the next family, but differing from them in being flat-
tened and keeled at the edges. Each capsule, on the average, contains
ten or twelve eggs. The drill ranges from Massachusetts Bay to Florid.i ;
north of Massachusetts it is rare and local ; yet a colony exists in the pj^-^ 4j3_ _ j^^^,
southern part of the Gulf of St. Lawrence, a fact which at once recalls sa^p^inx mierea,
the existence of oysters in the s.-une region.

In the Fusina3 the shell is spiiidle-shapeil, and the edge is never thickened so that
no v.arices are formed. Fusu,s contains a number of tropical and sub-tropical forms
in which the s|iindle shajie is especially well marked. The northern species, formerly
referred to this genus, are now referred to the next family. In the typical forms the
columella is smooth, a fact which separates it from Fasciolaria., in which it bears
oblique folds. Fasciolaria gigaiitea, which occurs on the southern coast of the
United States, is the largest known gasteropod, its shell reaching a length of nearly
two feet.

The BucciNiD^ is closely related to tlie Miiricidte. The spiral shell, instead of a
long sij)honal canal, has a notch through which the long siphon is extended. While
many of the included forms are very distinct, there are others which can scarcely be
sejiarated from the preceding family. This is especially true of a group of boreal
shells, represented on our coasts by the genera Keptunea and Sipho. Here the shell
is much like that in Fusics, and indeed, the species were formerly included in that
genus. JV. decemcostatus is marked with ten large revol\-ing ribs on tlie body whorl.
Sipho islandlcus is even more like a Fusus. Both are large shells occurring in
the cold deep water north of Cape Cod, reaching a length of nearly or quite three
inches.

Another problematical genus is Pi/ridK, with its various sulxlivisions, Fnhjnr, Sci/-
coti/pus, etc., some of which ]irobably lielong here, while others should be transferred
to the Muricidw, the Doliida% etc. In all, the shell is somewhat pear-sliaped in outline,
the spire being short, while the anterior end is greatly prolonged to correspond to the

332

LO WEli IN VER TEBRA TEii.

stem. Our two best-known species are Fahjur curica and Scijcotijpus canaliculatus.
The former is a lieavy shell with a short spire ornamented by a row of tubercles. The
latter is much more delicate, and is covered with a hairy ejiidermis, the sutures of the
spire being marked with a deep revolving channel. Tliese shells are both inhabitants
of water of moderate depth, coming to the shore only for the purpose of ovij)osition.
Their egg-cases, which are very peculiar, are frequently cast on the shore and attract
the attention of the most casual observer. They consist of a series of flattened mem-
branous capsules attached by one edge to a cord, and having op2->osite the point of at-
tachment a more transparent spot, indicating the place where the young are subse-
quently to make their exit. When laying these long strings, the snail goes beneath
the surface and as the ribbon begins to be formed, it appears above the sand, slowly

Fig. 4li.~ Pi/rula decussata, pear-snnil; a, dorsal, b, lower surface.

increasing in length, until the whole of its two or three feet of extent are formed.
Tiie first j)art of the cord is without capsules for about three Indies, then come a few
cases imperfectly formed. P2aeli capsule contains a number of eggs, and sj)ecimens
taken some time after oviposition show the shell formed, repeating in miniature the
essential features of the parent.

The name Fulgur (lightning) was a])plied on account of the zigzag brown streaks
with which young specimens (and older ones in warmer waters) are marked. Fulgur
carica is used extensively by fishermen as bait. Another species, living further south,
is noticeable fi-om the fact that it is reversed or sinistral, receiving on this account the
specific nnme perversa.

With the genus Buccinnm we take uj) a series of forms, whose position is less
doubtful than some of those just mentioned. Hucciniim is a northern genus of shells
covered with a horny epidermis, having a large aperture, a siphonal notch rather than

MOLLUSCS.

333

Fig. -115

- Buccuinm u/idatum,
whelk.

enouoli to crush the shell

a canal, a smooth columella, and an nntoothed outer lip. The most common species is
the whelk, _S. undatum, coninion to the northern Atlantic shores of Europe and Amer-
ica. It burrows in the sand below low-water mark. Its
eggs are laid in hemispherical capsules, yellow in color, piled
up in a heap, and presenting an appearance well described
by the name ' sea-corn ' apj)lied to them by the New England
fishermen. In England they are called 'sea wash-balls'
from the fact that they are employed in washing the hands,
their parchment-like texture tending to scour away the
dirt. Each capsule, when first laid, contains a number of
eggs, but of these but few develop, the others being swal-
lowed by the young which have got a little start in devel-
opment. In this respect, they are like the young spiders.

In America, the whelk is not used as food, but in Eng-
land large numbers are brought to the market, the annual
catch at Whitstable (a sm;dl village at the mouth of the
Thamesj being worth, in 186(3, fl'2,000. Although the
shell of the whelk is stout and strong, it is eaten in great
numbers by the larger bottom-feeding fishes, some of which

ai'e furnished with teeth strong

like a stone breaker, while others bolt shell and all whole,
leaving the gastric juices the labor of dissolving the
nutritious portions.

Besides the common Buccinimi ■undatum, several
other sjjecies are found in the north Atlantic, north of
the New England shores. One of these boreal forms, B.
ciliatiim, is figured ; the differences between this and the
common whelk are evident. Most of the specimens in
collections are obtained from the stomachs of fishes caught
on the Grand Bank.

Tlie genus Eburna embraces the ivory shells, so called
from the color and texture of some of the forms. In the
dozen oriental species comprised in the genus, the shell
is thick, deeply umljilicate, the columella and outer lip
without folds or teeth, and the suture between the whorls
channelled. The surface of the shell is i\'ory white,
spotted with an orange red. The animals usually move
along at a leisurely pace, but when alarmed they are ca])alile of much quicker motions.
They frequent muddy bottoms where the water is ten or twelve fathoms in depth, and
are caught in considerable numbers in the nets of the Chinese fishermen, who use
them as food.

JVassa contains a large number of species divided up into the sub-genera, Ili/anassa,
Tritia, etc. The general sha]ie and api>earance maj' be seen from our figures, a com-
mon character being the tooth or plait at the upjver part of the columella, much
more marked in some species than in others, and the extensive deposition of enamel
on the colnmellar lip, which not infrequently extends to a considerable distance out-
side the aperture. Most of the species are littoral, and at low tide our New England
flats are covered with myriads of JVassa trivittata and JV. obsoleta. Farther south a

Fig. 416. — Bucciiium c'diatum.

334

LOWER INVER TEBRA TES.

third species, N. vihex, becomes prominent. The trails of tliese species are common
on the soft mud, and frequently at the end will be found a little pellet of mud beneath
which the animal is hidden. All the specimens, however, do not bury
themselves at the retreat of the tide, as they are able to live for a con-
siderable time out of water. Possibly ISF. obsoleta is the more common
form. In this, the shell is dark brown, and ornamented by a net work
of reticulating lines. It does not thi'ive well where exposed to the ocean
Fig. 417.— .Vnssa surf, but prefers sheltered inlets, extending in large nuinbeis into inlets
where the water is decidedly brackish. In size it reaches a length of
about an inch. iV^ trivitiata is slightly smaller, and white or greenish white in color.
The third species, JV. vibex, is still smaller, reaching a length of half an
inch, and banded with ashy white and pale red, the colors being brightest
in the soutliern forms. All of the yassce are carnivorous, drilling holes
through the shell of other molluscs and then feeding on the flesh. They
are, however, not confined to living objects, for they will accumulate
in large numbers around any decaying crab or fish, and, together with fig. ns.—iVassa
the amphipods, soon devour all the fleshy portions. In Europe an
allied species, A^ reticulata is an enemy of the oyster beds, drilling through the shell
in a short time. They usually select the young oysters, but will destroy one three
years old in about eight hours.

The egg-cases of Nitssa obsoleta are among the most common of marine objects.
They are placed on any solid object that is handy, dead shells and the 'sand-saucer'
egg masses of A^f^fVv/ being most frequently used. The capsules are curiously fluted

and ridged, and are crowded together without order, each
attached by its own pedicel.

Purpiirn and its allies are by some i)laeed in the Muricidaj,
by others in the Buccinida^. In Pwyura the ajierture is
wide, the sjiire short, the whorls enlarging rapidly ; the col-
umella is flattened, and tlie outer lip is toothed. Purpura
lapllhis, a dirty white or ashen species, is common to the
shores of Europe and North America, thriving better and
growing to a larger size in the old world, where specimens
are frequently zoned with brown. On our own coast there is much variation in
appearance, individuals from the rocky coasts, where they are exposed
to the surf, having the ribs of the shell nearly smooth, while those from
sheltered localities have them roughened by scale-like projections. This
species does not range much south of Cape Cod, but north of that barrier
it is very common. It feeds on other animals, being especially fond of
the acorn barnacles {Balanus bahuioides) which flourish between tides.
The eggs are Laid in small oval capsules sujiported on slender stalks.
Each capsule contains numbers of eggs, only a few of which eventually
hatch, the others furnishing food for those that develop.

Purpurapatula was one of the forms which furnished the famous Tyrian ])urple,
the others belonging to the Muricidae. The animals were gathered in large numbers and
crushed, shells and all, in mortar-shaped holes in the rocks, two or three feet in depth.
From the bruised mass a liquid was obtained which was mixed with a small amount of
soda and diluted with several times its weight of sea-water. At first the fluid was yel-
low, but, after exposure for a time to the rays of the sun, it changed to purple. Then the

Fig. 419. — Purpura lapUlus.

Fig. 420. — Egg
capsules of Pur-
pura Uqnllus,
enlarged.

MOLLUSCS.

335

Fig. 421. — RMzochilus antipatharum, fastened to branches
of Antipathes ; on tlie right a young specimen.

wool was dipped into the dye for a few hours and taken out colored. During the
change in color a fetid odor like that of assafcetida is given off. To obtain the finest
color a mixture of two species of Purpura or Mttrex in certain i)roporlions was em-
ployed. For a long time the art of coloring with the secretions of molluscs was
entirely lost, but at the close of the middle ages it was rediscovered. Modern
chemistry has, however, replaced it, and now the use of mollusean dyes is nearly or
quite extinct.

In Couchole2Xis peruviana, the only species of the genus, the body whorl increases
so rapidly in size as to render the shell much like that of a lim|)et. This species occurs
along nearly the whole of the western
coast of South America, and is extensively
eaten by the Chilians and Peruvians. The
flesh is tough, and is beaten to make it
more tender. The sjiecies of liapatia
live upon coral reefs, feeding ujjon the
polyps. The genus RJdzochilus is notice-
able from the fact tliat the young of one
species has a well-formed shell much like
that of Rapana; but as the adult condi-
tion is readied it cements to the shell,
branches of the coral Antipathes or other
shells, or both, until at length all means
of communication with the exterior is by

means of the siphonal canal, the aperture being completely closed. What is the cause
of this peculiar self-immurement no one has yet been able to decide. Other species of
the genus are not known to possess such habits as those just described of R. antipath.-
arurn. In R. madfreporariurn the animal attaches itself to the larger reef-building
corals by means of the foot.

Another interesting genus is Magilas, the species of which all belong to the east-
ern seas. It is a fine examjile of that degeneracy which occurs in certain molluscs.
The young Magilus begins life as a well-behaved mollusc with a regular spiral shell;
but shortly it settles down on some growing coral, and then a race begins between the
two slow-growing forms. If Magilus kejit quiet and grew no further, a short time
would suffice to completely envelop him in the stony coral ; but, as soon as he is par-
tially covered, the whorls of the shell leave their spiral course, and grow out as an
irregular tube. As the coral grows, new additions are made to the shell, and the
neck-.and-ueck race is kept up until the mollusc or the coral dies. Soon the tube
becomes too long for the mollusc, and lie leaves the spiral ])ortioii and comes out to
live in the outer straight tube, filling uji the deserted whorls with a solid deposit of
lime.

In the CoLUMBELLiD^ the shell is oval, the spire moderately short, the aperture
narrow, and terminated by a very short anterior canal ; the outer lip is thick and
internally crenulated, while the columellar lip is toothed. The sjiecies are mostly
small, and many are brightly colored. On our eastern coasts several species occur,
among them Columbella avara, lunata, ornata, etc., while on the west shores the genus
is represented by four species. In the trojucs the number is much larger, some three
hundred being known from the whole world. All .are littoral, cnrnivorous forms,
abundant on seaweeds and hydroids, and in pools left by the retreating tides.

336

LOWER INVEUTEBRATES.

SuB-OrDEK III. — TOXIGLOSSA.

These animals are all predaceous and carnivorous, for which they are well adapted.
They have a strong proboscis, which can be extended some distance from the shell.
The lingual ribbon is armed with two rows of teeth, the middle or rhachidian series
being absent. The teeth are long and hollow, and it would ajipear that the animals
have the power to poison their prey.

The largest family, and the one best known to collectors, is the Conid^, which
receives its name from the conical shape of the sliell. The members ai'e almost all
tropical or sub-tropical, the number of species and the brightness of the colors increas-
ing as we approach the equatorial regions. Notwithstanding their carnivorous propen-
sities they are a]iparently timorous, preferring to live in holes in the rocks and coral
reefs, and retiring within the shell at tlie approach of danger. They crawl in a slow,
sluggisli manner, with their tentacles stretched straight out before them. Tlie only
genus is Conns, of which about three hundred species are known, most of them being-
inhabitants of the eastern seas, onl}' about fifty being found in'the tropical waters of
America. The general appearance of the animal may be seen from our figure of one

of an oriental species, Conus

textilis. The eyes are near
I be base of the tentacles, the
.oot is narrow and long, and
- furnished in the middle with
a large ojjening, the object
of which is frequently as-
serted to be the admission
of water to the circulatory
system. This connection of
the blood vessels with the ex-
ternal world has been lately
denied in any and all mol-
luscs, and apparently with
reason. Usually a small operculum is present, but not infrequently it is absent. The
shell is thick, cone-shaped, the s]iire short, ajterture narrow, the outer
lip sharp and neither toothed.

We have just referred to the fact that some, if not all, of the
Toxiglossa are poisonous, and the reader will doubtless pardon the
following quotation from the pages of Mr. Arthur Adams. Speaking
of Conns aulicus he says, — " Its bite produces a venomed wound
accompanied by acute pain, and making a small, deep, triangular
mark, which is succeeded by a watery vescielc. At the little island
of Meyo, one of the Moluccas, near Ternate, Sir Edward Belcher was
bitten by one of these cones, which suddenly exserted its proboscis as
he took it out of the water with liis hand, and he compares the sensa-
tion he experienced to that jjroduced by burning ])hospliorus under
the skin." In the South Sea Islands, Conus textilis and C. marmoreus are also con-
sidered as poisonous, though eases where their bite is fatal are rare and not well
authenticated. It is supposed tliat the teeth break off and are left in the wound.

Fig. 423. — Cmius
marmoreus.

MOLLUSCS.

337

A description of the more common species of cones would prove dull reading, and
so we merely mention the colors of the two species figured. Conns marmorevs is
dark or even black, marked with ti-iangles of white, while C. textile is very variable,
the general ground color being golden or orange, on which are laid brown reticulating
lines and white spots. The cones are favorites with collectors, and rightly so, for they
are among the most handsome of shells. Some of the species are very rare. Co?ius
gloria-maris, a white species with orange sjiots and triangular lines, has been sold for
two hundred dollars, while some of the rarer varieties of C cedo-nulli (a very variable
species) have brought over one hundred dollars. The former comes from the eastern
seas, while the latter is West Indian. Of course these prices do not
indicate any intrinsic value in the shell, but are merely indices of the
comparative rarity, and of the prices whicli rich collectors are willing
to pay for certain noted species. Other species equally rare would
not command a small fraction of these prices, merely for the reason
that they are not so well known, and dealers have not yet attempted
to speculate upon them.

The Terebeid^ contains about two hundred species of long,
slender, many-whorled shells from the tropical seas. They are readily
distinguished from other similar forms l)y the small apertui'e with an
anterior siphonal notch, and by the absence of true plaits on the
colmnella. The tentacles are short, and the eyes, when present, are
near or at the tips. The Terebras are known among the sailors as
auger-shells.

About as little need be said of the Pleueotomid.e,
ill which tlie shell is si)indle-shaped, the aperture pro-
longed anterioi'ly while near the suture there is a notch.
An operculum is not always present. Although some
five hundred species are known, but little of poijular
interest can be detailed concerning them. The genus
Pleurotoma is represented on our eastern shores by a
few small and inconspicuous species usually assigned
to the sub-genera Bela and 3I(ingelia, while on the
Pacific coast the species are about equally numerous.
In the West Indies and at Panama many more forms
are found.

The Cancellarid^e differ from the other Toxi-
glossa in being vegetarians, and they differ further in having the pro-
boscis rudimentary. The shells may lie recognized by the folds on the
columella and on the outer lip, and the fact that the shell is almost
always marked off into squares by transverse ribs and revolving lines
which gives rise to the name of the principal genus Cancellaria. The species live
in comparatively shallow water, though they are but very rarely found above low-water
mark. In the northern Atlantic the family is represented by a small white shell
about half an inch in length, known as Achnete viridida. No specimens are known
to have come from south of Cape Cod.

Fig. 424. — Ttidiiu
oculata.

Fig. 423. — Pleu-
rotoma baby-
lonia.

VOL. I. —22

338 LOWER INVERTEBRATES.

SuB-OkDER IV. — T.ENIOGLOSSA.

The Taenioglossate Mollusca are Largely marine, though one or two famihes are
found in fresh water. The shell is sjiiral, though in a few forms this appearance is
obscured. The lingual ribhon in most forms has the shape of a band, and is armed
with seven teeth in a transverse row, though in a few forms here admitted there are
nine, while in others the number is reduced to three, and occasionally all are absent.
Two tentacles are always present. In some the aperture is entire, and in others it is
notched or produced into a canal for the resj^iratory sijjhon. We will first consider
the holostomate (entire mouthed) forms.

Our first family contains the periwinldes, the Littoeixid.e of scientific nomencla-
ture. This latter name is very approjjriate, for they are all shore-living forms. The
shell is ovate, with a short, sharp spire, and a round mouth which is closed, on the
retreat of the animal, by a horny operculum. They have a thick foot, large snout,
and the eyes are jjlaced at the base of the antennie. They live on the
shore between tide marks and feed upon the smaller alga?. The principal
genus is Littorina. The first species which we will mention is the peri-
winkle proper, L. litorea, the mollusc that is eaten after being extracted
from its shell by a bent pin. Our figure represents the species (which
is one of the largest of the genus) natural size. The shell is solid and
m'aiiforea'xivvi- Very variable in color. Some are banded and some a uniform tint of red,
^" "' brown, or black, the darker colors predominating. The advance of this

species on our shores is very remarkable. It is a native of Europe and was first noticed
at Halifax several years ago. In 1870 it had appeared on the coast of Maine. In 1872
it had reached Massachusetts, but it did not apjjcar south of Cape Cod until a year or
two later. Now on both the northern and the southern shores of New
England it is one of the most common molluscs. In England it is ex-
tensively used as food, the annual catch amounting to many hundreds
of tons. It is prepared by boiling, then the oi)erculum is )iulled off and
the meat extracted from the shell. In taste it is much like the clam, ^fo'rmamdfs!'
only far more delicate. Though very abundant it has not yet acquired
any economic importance here, as the American peoj^le seem greatly a-\erse to trying-
experiments in the gastronomic line. Were it better known, it would be appreciated.
Another species which is common to both continents, L. rudis, has received nearly
twenty specific names on account of its variations and its extensive range. The gen-
eral aii])earance of the shell may be seen from our figure, but the color is variable.
Usually it is yellow or olive-green, and without markings, but occasion-
ally specimens are found banded or blotched with some lighter color.
Until the advent of L. litorea, Littorina polliata was the most abundant
species on the New England coast. The shell may be either plaiu or
^torwm^pduiata. variously Ornamented with bands and blotches of color, — white, green,
or brown. It is common on rocky shores, and is especially fond of creep-
ing over the I'ock-weed {Fucus) or eel-grass {Zostera). Further south the common spe-
cies is Z. irromta, which is a little lai-ger than i. litorea, but is longer and has a more
acute spire. It is comparatively rare in southern' New England, its metropolis being-
further south. Its introduction into the waters of Long Island Sound may have been
with oysters transplanted from the Chesapeake.

MOLLUSCS. 339

Another member of the family wliich should be mentioned is Lacuna vincta. It
lias a thinner and more slender shell than any of our Littorinas, and is reddish or horn-
colored usually, with two or more darker reddish bands, which follow
the spiral of the shell. Like the rest of the family, it is a vegetai'ian,
feeding on algiB.

Closely allied to the Littorinidoe is the Rissoid^, which needs but a
passing mention. The family, and its principal genus, iJiissoa, derive their ^'''^naij^cta^"^
name from Risso, a naturalist who in the early part of this century studied
the fauna of the Mediterranean. Some of the members inhabit the sea, while others live
in brackish water, or even in that which is entirely fresh. In all, the sj)ire is long, the
lip thickened, and tlie aperture rounded. IlissoeUa, which is found in Europe and
Japan, lives between tide-marks. The shell is very thin, and the ejes, which are placed
upon the surface of the head, are " so far behind the tentacles that the transparency of
the shell seems to be essential to the vision of the animal." The s2)ecies uf Jiissoa are
numei'ous, sevei-al being found in American waters. BytJiinia is one of the most
prominent of the fresh-water genera. Its fifty species belong to the eastern hemisphere.
In the United States, Amnicola is distributed through all parts of the country, the
small species living in fresh water. They were formerly included in the Paludinida3.
Potnatiopsis should be mentioned, from the fact that the species are air-breathers.

The Cyclostomidje are exclusively terrestrial, and were formerly included among
the Pulmonata. Like the members of that order, they breathe the air by an essen-
tially similar pulmonaiy organ, but in the rest of their anatomy they deserve a. place
where we have put them. This is one of the many instances where a too close atten-
tion to one organ or one physiological operation would lead to erroneous ideas of rela-
tionship. Still the other process is next to impossible, and on this point we can do no
better than quote the words of Fritz Milller : " Of a hundred who feel themselves
eom]5elled to give their systematic confession of faith as the introduction to a manual
or monographic memoir, ninety-nine will commence by saying that a natural system
cannot be founded on a single character, but has to take into account all characters,
and the general structure of the animal, but that we must not sum up these characters
as equivalent magnitudes, that we must not count, but weigh them, and determine the
importance to be ascribed to each of them according to its physiological significance.
This is probably followed by a little jingle of words in general terms on the compara-
tive importance of animal and vegetative organs, circulation, respiration, and the like.
But when we come to the work itself, to the discrimination and arrange-
ment of the species, genera, families, etc., in all probability not one of
the ninety-and-nine will pay the least attention to these fine rules or
undertake the hopeless attempt to carry them out in detail." IsTot-
^^°'ttma'bim.''''"^' withstanding this melancholy picture, science is constantly striving to
arrange the groups of animals and plants; facts of structure are
weighed, and it is by just this process that the CycIostomid;p, a family without gills
and with a pulmonary respiration, are accorded a position here among the branchiate
molluscs.

In this family the whorls of the spiral shell are rounded and the aperture is circu-
lar, hence the family name. As in the branchiate forms with which they are associ-
ated, the members of the family close the shell by an operculum which is round and
increases in size with the growth of the animal, the new additions being placed in a
spiral manner, the nucleus being central. The animal is much like that of Littorina ;

340 LOWEM INVERTEBRATES.

it has a long proboscis and two contractile feelers, with the eyes at their bases. The
lingual teeth are seven in a transverse band.

The Cyclostomes are largely tropical, but very few- species straying into temperate
regions. They live in damp places, some on the ground, some in trees, while others
are found far from the sea. Over a thousand species have been described. Some
have a peculiar gait ; the foot is divided into halves by a longitudinal furrow, and in
walking the animal advances one side and then puts it down, then the other side is
moved forward in the same way ; the two sides corresponding to the two feet of man.
The piincipal genera are Ci/clostoma, Ct/dophortis^ Cydotus, and Vliondropoma.

In the AcicuLiD^ the shell is nearly cylindrical, the margins of the aperture being
nearly parallel. From the wave-like motion witli which they progress, they have been
termed ' looping-snails.' The species are amphibious, and live among the sea-weeds
thrown up on the shore, or in shallow water. The species are small. The only genus
which needs notice at our hands is Truncatella, in which, as the animal approaches
maturity, the upper parts of the spire are broken away and the animal repairs the
damage by closing up the broken whorls by a calcareous de])osit. On account of this
truncation of the shell, the genus has received its name. The family contains about a
hundred species, mostly from the troj)ics.

The Paludinid^ shares with the Limnasida', ali-eady mentioned, the common
name, ' pond-snails.' Its mnubers are widely distributed through the temjierate zone
of the northern hemisphere, but few being found within the tropics. They live in
muddy ponds or streams, where they crawl slowly over the bottom
or even burrow in the soft mud. The foot is large and broad, a
well-developed proboscis is present, and the long cylindrical ten-
tacles bear the eyes on little projections near the base. The water
required for res])iratory pui-poses is conveyed to the gills by an
interesting contrivance. On either side of the neck are developed
little fleshy outgrowths which, together with the mantle, form
'terie'xTa, showing res" little tubes. In the adjacent figure these are seen on either side,
piratory tubes. projecting a little outside the shell. The water goes in through

the right tube, passes over tlie gills, and then is forced out through the tube on the
left.

The sexes are distinct, and the young are brought forth alive. The eggs undergo
their development inside of the mother, and in the species with thin shells they may
occasionally be seen inside the body. The development requires about two months,
and at the end of that period the young are sent forth, three or four at a time, to
begin life for themselves. The shells are thin in some forms and niore solid in others ;
the prevailing color is some shade of green or greenish bniwii, banded with darker,
though sometimes the bands lacking.

The principal genus, Paludma, has been divided u|) into several sub-genera, of
which Melantho and Tulotoma are strictly North American. A curious instance of
the fact that a low temperature, which affects so greatly the land shells, has but little in-
fluence on the size of fresh-water forms, is found in the case of Paludina ttsstiriensis,
the largest Siberian species, which occurs in a latitude but little south of the line of
perpetual frost, and where the n\ean annual tem])erature is the same as in Iceland.
On the other hand, recent explorers have brought home large species found in the
lakes of Centr.al Africa. No species have as yet been found in Australia, New Zea-
land, Polynesia, or the West Indies.

AMERICiuN POND SNAILS.

1. Paludina decisa. 2, 3. P. intertexta. 4. P. coarctata. 5. P. georgiana. 6. P. contectoides. 7, 8. P. In-
tegra. 9, P. subpurpurea. 10, 11, 12. P. ponderosa.

MOLLUSCS.

341

The Melanhd^ are also fresh-water inhabitants, in which the shell is covered with
a thick epidermis, which, in some species, is so dark that the family name [melas,
black) is very appropriate. Others are brown or dark green. The shell is usually long,
turreted, or conical, with a small mouth. The foot is large and triangular, the proboscis
short but stout, and the eyes are near the bases of the tentacles. The family is readily
separable into two sub-families, both on structural characters, and on geographical
distribution. The first, the Melaniina?, are oriental, only a few being found on the
North American continent. In these, the aperture is usually broadly rounded and

' JLl

llL.. 1^-. !■:

not produced in front, tliuugh often channelled or notched, while the margin of the
mantle is fringed, and many of the species are ovo-viviparous ; that is, the eggs under-
go their development and are hatched outside the parent. In the other
sub-family, the StrepomatinsE, the margin of the mantle is plain, and the
eggs are laid and attached to stones and plants. With three or four ex-
ceptions, all the Strepomatinse are confined to the United States, a few
extending to the West Indies.

Of the Melaniinse, the most prominent genus is Melwiia, which eon-
tains about four hundred species, mostly distributed through Asia and
Polynesia, though a few are found in tropical America and southern
Europe. In many of the specimens the a])ex of the shell has disap-
peared, owing to the erosive action of the water which they inhabit.
Mekmo^Mis costata, a common Syrian species of a genus allied to
Mdania, is said to inhabit the Dead Sea, the only exception, so far as I am aware,
to an exclusively fresh-water habitat in the family.

Fig. iXi. — Pleu-
rocera pallidum.

342

LOWER INVERTEBRATES.

Of the Strepomatina^, about five hundred nominal species have been described,
but uutil we know more of the anatomy, the life history, and the variations of these
forms, nothing definite can be known of their classification. Here is a wide field for
study open to those students of the centi'al jiortions of the United States, which will

Fig. 434. — Anculotus
prcEi'osa.

Fig. 435. — Anai-
lotus plicata.

Fig. 436.— ii^ft-
asla fuliginosa.

Fig. 437. —Gonio-
basis depi/gls.

Fig. 438. — GoHio-
basis impj-essa.

be productive of great results. Of the development we know absolutely nothing, not
even if a veliger is formed. Ten genera and sub-genera are recognized, and the great
bulk of our species come from the Ohio River and its tributaries. Species of Ancu-
lotus are found in the Potomac and Susquehanna, while others of the family have been
introduced into the Erie Canal. None are known to occur naturally in New England,

though a few years ago some were introduced into Lanes-
boro (Mass.) pond, where they appear to thri\e.

Of tlie species we have but little to say, and will simply
let our figures, which represent the prominent genera, speak
for themselves. The first species of lo described was re-
garded by the early American naturalist, Thomas Say, as a
fresh-water species of the genus Fiisun, with which it has in
reality nothing to do. All of the species of this genus occur
in a very limited tract, and have so far been found only in
the mountainous regions of western Virginia and eastern
Tennessee. Most of the other genera have a rather re-
stricted distribution, Goniobasis being the most widely dis-
tributed; it contains over half of the known species. Schi-
zostoma is very similar, but may be sepai-ated by a notch on
the posterior edge of the outer lip, jirodiiced in some way
as yet not understood. This genus occurs only in northern
Alabama, in the streams which flow into the Tennessee River.

The Pteamidelltd.-e is a small family of marine molluscs, with a
long, slender shell, in which the columella has frequently one or more
prominent folds; the eyes are sessile, the proboscis retractile, and the
tentacles either broad or long and slender. Tu many the lingual teeth
have entirely disappeared, owing to their parasitic habits.

Pyramidella is a tropical genus of littoral molluscs, tlie members of ^^^ m.-Schi-
which burrow along just beneath the surface of the mu<l. The members |';^';™" »«'*-
of the allied fossil genus Nerincpci. were much larger than any of the ex-
isting members of the family. The species of Odostomia are numerous and widely dis-
trilwted, the genus being represented by several species on our coasts. Some of these
usually live beneath stones, moving in a very slow manner, while others are usually found
on the shells of scallops {PecUn) and but rarely anywhere else. Whether they live a
semi-parasitic life or are commensals has not been settled. Stylifer is much more of a

Fig. 430. — lo sp'mosa.

MOLLUSCS.

343

parasite, and it is a curious fact that all the parasitic Mollusca affect only the echino-
clerms and coelenterates. On our New England coast aS'. stinqisoni occurs on the com-
mon sea-urchin, Stroiujylocentrotus; in England Stylina turtoni also affects sea-iu'chins ;
a Mediterranean species lives firmly attached to the anal tube of the feather star, Com-
atida ; while, to mention but one more sijeoies, 8. astericola, as its name implies, dwells
on starfish. Some of these forms are true parasites. With their slender foot they obtain
an entrance between the calcareous plates of the starfish or sea-urchin, and there they
live on the juices of their host, only the apex of the shell being visible from the
exterior.

In Eulima the parasitic habit is carried still farther. Most of these live on holo-
thurians, although some attack starfishes. They even enter the alimentary tract of
some of the sea-cucumbers, where they feed on the food of the host. One species has
become so modified 1)}' parasitism that, though it still retains a shell, it has lost many
of its distinctive molluscan characters. This species, as described by Semper, lives
on the outside of a species of holotliurian, and its proboscis is enormously developed
so tliat it pierces the tissues of its host ami enters the cffilomatic cavity. Feeding
thus on the fluids of the sea^cucumber, it has no need for teetli, and hence its lingual
ribbon has disappeared, and from the same cause, disuse, the foot and eyes have fol-
lowed a like course. Our American Eulima oleacea does not seem to have carried its
parasitic habits so far. It occurs on the skin of Thyone hriareus, a common holothu-
rian south of Cape Cod.

It is doubtless the fact that it lives a ]iarasitic life that has led some naturalists to
place that most degraded of molluscs, Entoconcha, in this family. Not enough is
known of it to warrant such a position on any other ground. It is referred to on a
previous page (p. 297).

The TuRRiTELLiD^ embraces forms with a shell much like that of the Pyramidelli-
diE : long and turreted, with a round mouth which is not notched or produced into a
canal. The operculum is horny and many-whorled. The animal has a moderate, but
short foot, a short muzzle, and the
eyes are placed at the outer base of
the tentacles. The margin of the
mantle is fringed. Nearly a hun-
dred sjjecies are known, all from
salt water. Most of them are cov-
ered with a brownisli epidermis.

Closely allied to the last family
is the Vermetidve, some of the mem-
bers of which recall the Serpula
among the worms (p. 227) on ac-
count of the irregularity and ver-
mian shape of the shells. The ani-
mal has an elongate head l)earing
two long tentacles. The shell be-
gins as a regular spiral, but after a
few turns the regularity is lost, and
the tubular shell grows in any direc-
tion, the spiral character almost entirely disappearing. The shell gi'ows more ra]iidly
than the animal, and, as a result, the posterior portions of the tube are partitioned

Fig. 441. — i'ermettis lumbricalis.

344

L 0 WER IN VER TEBRA TES.

off by a calcareous deposit, thus giving a ready means of separating the shell of the
mollusc from that of the worm. In Vernietus the shell is entire, but in tSiliquana
the tube has a longitudinal slit. Ccecum is usually placed here, but it differs
greatly in its lingual dentition, only two lateral teeth on either side being present, and
the rhachidians are absent. Tiie shell begins as a spiral, but with growth the older
portions are lost and the shell becomes simply a curved tube embracing an arc of from
sixty to ninety degrees. Both Termetus and Ccecum are represented on the shores of
the United States ; the species of the latter genus are very minute, and in assorting the
contents of the dredge they readily escape notice. Some of the Vermetidse become
attached to sub-marine objects, while others are always free. Specific limits are not
very well defined, owing to the irregularity of the shells.

The apple-shells of dealers belong to the family Ampullariid.e. These live in
tropical cotmtries, where they replace in the jwnds and marshes the Paludinida° of
more temjierate climes. Africa .and Soutli America seem to be especially favorable to
their gi-owth, and from these regions we have the finest specimens. They are an am-
phibious group, living apparently equally well either in or out of the water, yet they
require a certain amount of moisture for their well being, and when their native
marshes dry up they burrow deep into the mud. They are well fitted by nature for
their amphibious life, for they have both lungs and gills. The lung cavity is placed
above that which contains the gills, but the two are connected by means of an o])eniug
through the fleshy partition. This structure enables them to breathe either air or
water, and Professor Carl Semper, of Wiirzburg, who spent a long time in the Philip-
pines, frequently observed " that the Ampullar ice breathe not only with both gills and
lungs, but they do so in regular alternation ; for a certain time tliey inhale air at the
sur^ice of tlie water, forming a hollow elongated tube by incurving the margin of the

mantle, so that the hollow surface is closed against
the water and open only at the top. When they
have thus sucked in a sufficient quantity of air,
they reverse the margin of the mantle, opening
the tube, into which the water streams. The
changes are tolerably frequent, once or tAvice in
a few minutes, depending probably on the tem-
perature."

The apiple snails are long-lived, and specimens
have been brought to northern climes hidden in
the liollows of logs of mahogany from Honduras,
cut no one knows how long before. Mr. Laidly,
who lived for many years at Calcutta, tried many
experiments with them, and some specimens
which were confined for five years in a dr.awer
were alive at the end of that period.

The shells are large, thin, and globular, cov-
ered with a glossy epidermis, and closed by a
horny operculum. The eyes are good-sized, and
are placed on short stalks, and the tentacles are very long and slender. The eggs are
large and spherical and are laid upon the stems of water-plants in large bundles, fur-
nishing many a meal for the marsh birds. The most ])romincnt genus is Ampulkn-ia,
in which the epidermis is usually green, and the respiratory tube long. The South

Fig. ^2. — AmpiUlaria canaiiculas, apple snail.

MOLLUSCS.

345

Americans call them idol shells. A few species are found in the southern portion of
North America, living in the rice swamps of Georgia, etc.

The family Valvatid^ embraces a few small fresh-water shells, usually associated
with the Paludinida\ The shells are discoidal or conical and are usually covered with a
greenish epidermis. The animal has a small foot, and when in motion the delicate bran-
chial plume is extended outside the gill cavity, and may be seen, an object of beauty,
above the neck. The si)ecies are distributed through the temjiei-ate
regions of the globe, frequenting slow-running rivers and ponds. They
are hermaphroditic ami lay their eg;os in a single caiisule attached to Fig. 443. — ra;-

^ •' °° ° ' . rata.

Stones or to aquatic plants. Valvata, the only genus, has been divided
into three or four sub-genera. Our tigui-e re]iresents Valvata tricarinata, a common
species in some jiarts of the United States. Other forms have the whorls rounded
instead of angular.

We have already referred to some of the limpets on a preceding page, but it is ex-
tremely doubtful if all should be included in the Zygobranchiate Mollusca and if any
value is to be placed on lingual dentition, some of them should be assigned a position
here. We have already mentioned the AcM-EiDJi, and would merely state that usually
they are considered as closely allied to the Calyptr^eid^ which
will receive brief mention. In this family the shell is limpet-like
and with the beginning somewhat spiral. In some the spiral is so
far developed as to form a partial partition (cohunellar lip) so that
the common name ' slipper-lim]iet ' is very appropriate. In othei's
the interior of the shell is simple. Unlike the other limpets pi-e-
viously mentioned, these forms are sedentary, and most of them
never seem to leave the spot where they settle down in early life.
That this stationary habit occurs is shown l)y the shape of the
shell, which is always moulded to fit any irregularities of the sur-
face to which they are attached. Thus, when on an oyster shell,
the edge of the slipper-limpet reproduces (of course reversed) all the elevations and
depressions of the other. With this stationary life it is not readily seen what they
live upon, unless it be the microscopic life so abundant in the sea water, for they can-
not move far to obtain the attached alga?. In confinement some have been known
to devour animal food.

The genus Crepulida departs but little in coiiehological characters from the type
usual in the univalve molluscs. The general appearance may be seen
from our figures, which rejn-esent two of the common American forms.
The aperture is divided by a posterior lamina (the cohunellar lip) so
that the resemlilance to a slipper is striking, whence the
common name, slipper-limpet. These forms are almost
always found attached to the shells of other molluscs,
the otiter part of the aperture of JSTatica and Nassa, when
inhabited by hermit crabs, being a favorite place. Why
this association of forms should exist has not been ex-
plained; ]iossilily the erumlis dropped from the hermit's dinner may
afford abundant food for the limpet. Frequently several individuals are
placed one above another, the lowest one adhering to some living or dead
shell or to the king-crab {Limulus).

The, genera Calyptraio, and Crucibulum are known as cup-and-saucer limpets. In

FlLi. 444. — Crepidula
foniicata, slipper
limpet.

Fig. 445. — Crepir
dula plana.

Fig. Ua.— Cruci-
bulum striatum^
cup-anti-saucer
limpet.

346

LO WER INVER TEBRA TES.

Fig. 447. — Natica heros
crawling, showing tlie
very large foot.

the centre of the inner surface of the shell is a calcareous cup, the shell proper corres-
ponding to the saucer. In habits the members of these genera are much like the
species of Crepidula. Among the other genera of the family
may be mentioned In fundi bidum, (Japidus, and Hipiwnyx.

The Naticid^e are carnivorous marine snails with globular
shells and an entire half-moon shaped aperture, the outer lip of
which is sharp, while the inner one is usually ornamented with
a callus deposit which is frequently thick and extensive. The
animal has a very large foot, and, when extended, broad folds
nearly or quite envelop the whole shell. The tentacles are
small, slender, and widely separated, though connected for a
[lortion of their length by a fleshy membrane arising from the
top of the head. Eyes may be present or absent ; when present
they are placed at the base of the tentacles.

The genus JSfatica, with its two hundred s]iecies, is distrib-
uted all over the world. It has been divided into the sub-
genera Neverita, Lunatia, Mamma, Amaura, etc., which need
not be characterized here. All are active ])redaceous forms,
living by preference on sandy bottoms and shores, often stray-
ing above low-water mark so that they are left exposed by the
receding tide. At such times they usually burrow just be-
neath the surface, creating a little hummock of sand.
In northern New England the most common species
is Natica (Lunatia) heros. It is there the largest
littoral univalve, the shell in large sijecimeus attain-
ing a diameter of three and a half and a length of
five inches. In color the adult shell is ashy gray or
brownish, the inside of the aperture being reddish ;
but the young are frequently marked with three
rows of dark, usually reddish spots. This was for-
merly regarded as a distinct species under the name
triseriata. South of Cape Cod Natica {Neverita)
duplicata is fully as abundant as the species just
named. It may readily be distinguished by the
callus which in this species completely covei-s the
umbilicus, as shown in the cut. Natica /teros ex-
tends south to Georgia, and N. dtiplicata has been reported from Mexico and Yucatan.
Several other species of the genus are found on our eastern coasts.

The food of Natica is mostly bivalve molluscs. Burrowing through the mud, the
snail runs across some unfortunate clam, and immediately the siege begins. Close its
valves as tightly as jwssible, the clam is not secure ; for the snail lirings its well-armed
lingual ribbon into play and by drawing it across the shell, slightly rotating the body
meanwhile, it rasps away a portion of the hard calcareous armor, and in time it makes
a hole through to the soft jiarts, which are then devoured. The hole through the
shell is almost jierfectly circular, and is bevelled like a countersunk hole made by
the artisan.

The egg masses of the Naticus bear the common name sand-saucers; they are
among the most abundant objects on the sea-shore during the sjiawning season. The

Fig. 44S. — Natica heros.

MOLLUSCS.

347

general shape is shown in the figure ; it is somewhat like a saucer without a bottom,
but the two ends of the ribbon are not united. On holding one up to the light, the
numerous eggs are seen as light spots arranged in quincunx. For a long time these
sand-saucers were a puzzle to naturalists, and under several different names they were
regarded as Polyzoa. The peculiar shape of the ribbon is due to the method of its

Fig. 449. — Sand-saucer, egg mass of Natica lieros.

formation. As it passes out of the jjarent it passes over the foot and is pressed against
the body of the shell. At first it is soft, gelatinous, and adhesive, but soon it hardens
and unites firmly to the surface some of the surrounding sand. Mr. A. H. Tuttle has
recently studied the develojiment of these eggs.

The shell of Sigarettis is much like that of Haliotis, but lacks the series of perfora^
tions characteristic of that form. The species
frequent sand flats in the warmer waters of the
woild, where they ci'awl in a sluggish manner
searching for food. Tliey ai-e very timorous
and retract themselves on the slightest alarm ;
but, owing to the large size of the ajierture and
the minute operculum, they are not much better
off after having withdrawn themselves as much
as possible into the shell. Lamellaria, in shape
of shell, holds a position about midway between
Ncitica and Sigaretus., but has no operculum.
Only ten species are known, none of them from
America. The following observations ap})l}' to
L. perspicua, a European species. The time of
spawning is during February and Marcfi. At

that time the female eats a round hole in the colonies of one or more species of com-
pound ascidians, this it lines with a pot-shaped capsule furnished with a transparent
lid. In this the eggs are placed, and, as they increase in size, the whole nest rises up
beyond the surrounding portion of the ascidian. At last the embryos are ready to
liegin their free life, and then the lid bursts open and out come the young. By some
tiie genus Entoconcha is placed in or near this family.

With the family Cerithiid^ we return to a group of molluscs with long and
slender shells, resembling in many respects the Melanians, but in others departing
considerably from them. The shell is long and many-whorled, the aperture with an
anterior canal and a second less distinct posteriorly. The proper habitat of the
family is in the tropics, though nunu'rous members are found in colder waters. Some
of the species are marine, some live in brackish water, while others inhabit streams

Fig. 450.

348

L O WER IN VER TEBRA TES.

Fig. 451. — PotamUles
telescopium.

and ponds. The species of Cerithium are numerous and variable, and it is said that
it was the difficulty of classifying the species of this genus that first led Lamarck to
speculate upon the origin of species. Our species are mostly placed among the sub-
genera Cerithiopsis, Bitthtm, and Triforis. They are all marine. The species of the
latter have reversed shells, and one ( T. nigrocinctus) is abundant
on bottoms where the algas are numerous.

The fresh and brackish water species are mostly ]>laced in the
genus Potmnides, of which Pyrazus, Telescopium^ and Ceritlddea
are to be regarded as sub-genera. The fifty known species are
mostly from the eastern hemisphere. The brackish-water species of
the East Indies frequently leave the water and climb on the roots
and branches of the mangrove trees, suspending themselves by glu-
tinous threads. The Malays are fond of P. telescopium and P.
palKstre, which they cook by throwing them on their wood fires.
The bent pin, so usefid (according to Dickens) in extracting the
meat of the periwinkle, would here avail but little, on account of the
numerous whorls ; so the natives break off the apex of the shell and
then suck the animal through the opening thus made. The individ-
uals of this genus are very numerous in suitable places, and near
Calcutta Potamides telescopium is so abundant that the shells are
gathered and burned for lime, the animals being previously killed by exposure to the
sun.

The cowries, or porcelain sliells, are known in scientific nomenclature as the Ctp-
E^iD^. Like the cones, they are favorites with collectors, and a drawer filled with
their enamelled and brightly-colored
shells is a beautiful sight. By char-
acters derive<l from the shell they are
readily distinguished from all other
molluscs, for the spire is nearly or
quite concealed by the body whoi'l.
The aperture is long and narrow, ter-
minating at each end in a notch, whiK'
the lijis are usually toothed, the outer
one being thickened and rolled in-
wards in the adult, though in the
young it is thin and sharp, and the
spire is visible. The animal has a
broad foot, while the mantle is ex-
panded on either side so as to form
broad lobes (usually fringed on the
margin), which turn up over the shell.
When full grown these lobes secrete the shining enamel which covers the entire ex-
terior of the sliell and obscures the sinre. The line where the lobes of the mantle
meet upon the back is usually marked with a lighter line.

The principal genus, CyprcBO, contains about two hundred tropical and semi-
tropical species, only a few of which occur in the Atlantic, the great majority being
from the East Indies and the islands of the Pacific. In habit some are retiring, hid-
ing themselves under stones and among the branches of coral, while others crawl

Fig. 452. — Ct/prwa ajv/((5, eyed cowry.

MOLLUSCS.

349

about, exposed to the full i-ays of the sun. They are littoral animals, occurring most
numerously near or just below low-water mark. The colors of the shells are bright,
or are laid on in pretty and striking patterns, while the animals are, if
possible, even moi-e beautiful than the shells. Some of the species are
among the couchological rarities, and for them, in times
[last, enormous prices have been paid. The rarest species
(or at least the highest priced ones) are C. (juttata and ('.
princeps. Certain species have always been highly prized
l)y savage races, and Ci/pnea nioneta, the money cowry,
passes, or used to jiass, as the current medium of exchange
among some of the African tribes. It is a native of the
Pacific Ocean, and is brought in large numbers to Eng-
land and tlience shijiped to Africa to be used in barter.

Among the sub-genera may be mentioned Trivia, Lti- ^^%^^'g~J'^a'''"'

po7iia, and Aricia, C. moneta being a rejiresentative of

the latter. Trivia strays into northern waters, one species being found

FiG.454.— Trivja jjj Eni-Qijean seas, while another is found in California. The sub-genus

Luponia is also represented by two species in the latter region. All

the species of Cyprma are carnivorous, and they eat living or dead food.

The species of Ovulum are to be recognized by their elongate shell, which, in some
forms, is greatly drawn out at the extremities, as in the weaver's-shuttle shell, O. volva,
from the Philippines. These shells are not so ]>rettily marked as the cowries are, but

Fig. iz<i>, — UciLlum volca, we.iver's shuttle shell.

are usually more or less unicolored, and the color sometimes corres))onds to that of
the surroundings, and the Floriilian species, Ovulum vnipHcatum, is said to be yellow
or purple according to the color of the gorgonid corals on which it dwells, and on
which it is supposed to feed.

The Strojibid^b I'eceive the common name, wing shells, on account of the broad
wing-like expansion of the outer lip in some of the species. Other
common names are applied to some of the members of the family.
The animals are among the most active of the molluscs. The long
and muscular foot is divided into two halves, adapting it for pro-
gression by a series of leaps instead of the ordinary creeping motion.
The operculum is also an aid in locomotion ; it is claw-shaped and
toothed on the outer edge, and these serrations are used to obtain
a foothold. Then the foot is straightened l)y a violent muscular
action, and the animal jumps forward. The other parts are
equally well developed, and seem to demand for these animals
a place near the toj) of the gasteropod series. The eyes are large
and placed at the extremities of the thick stalks, while the ten-
tacles are long and slender, the tentacles and eye-stalks being united for a portion of
their lenarth. The muzzle is long and extensible. The strombs are carnivorous and

Fig. 456. — Strombus
pugilis.

350

LOWER INVERTEBRATES.

scavengers, feeding almost entirely on dead and decaying animal matter. The shell
has a sharp conical spire, the outer lip is expanded, and usually is notched near the
anterior canal.

The genus Stronibus has the outer lip entire, with the exception of the notch

mentioned above, and the aper-
ture is long and narrow. In the
young the outer lip is small, and the
shell looks like that of a cone, but as
the period of maturity is a]iproached
it becomes flared out. Species of
the larger wing-shells are among
the most common ornaments, large
numbers being brought from the
West Indies. In the United States,
the species most commonly seen is
Stro7nbus gigas, a West Indian form,
with a delicate red or pink intei-ior.
As the name indicates, this is one of
the largest members of the genus.
Another species common on the
Florida reefs is S. pugilis, the gen-
eral a])pearance of which may be
seen from our figure.

Allied to Stromhus are the scor-
jiion shells forming the genus Ptero-
cera. In early life the shells are much like those of the strombs, but when approaching
the adult condition the long finger-like processes of the
mantle liegin the secretion of shelly matter, so that the
outer lip is armed with a number of strong horns. At
first tiiese horns are channeled, but later in life thej' be-
come solid. In some they are short and straight, but in
others they are considerably bent. All the species come
from the Indo-Pacific regions. In BosteUaria, which has
much the s.ame distribution, the shell is much like that of
Fusus, the spire and the anterior canal being longer than
in Pteroceras, while the horns of the aperture are very
much smaller. Postellaria moves about in the same
manner as do the strombs, but some species are more
timid. It is an inhabitant of deeper water than the
other. The only other oriental genus which we will
mention is TereheUum the species of wliich live in deep
water. They are very active and at the same time very
timorous. "It will remain stationary for a long time
when, suddenly, it will roll over with its shell, and con-
tinue again perfectly quiet." At other times they will

leap several inches from tlie ground, like species of Stromlms. In some species one
of the ocular peduncles is longer than the other, and this one is used almost exclu-
sively. As in the strombs, the iris is colored and the i)U2Jil black. Aporr/iais con-

FiG. 457. — Strombus lentiginosus.

Fig. 458. — Pteroctra cluragra, scor-
pion shell.

MOLLUSCS.

351

tains but four living sjjecies, one of which, A. occidentalls, is occasionally found off
our northern coasts. Of its habits almost nothing is known. In the pelican's-foot
shell {A. pes-pelecani) of Eurojio the outer \i\i is produced
into two or three long horns, like those of Pterocera.

The helmet shells, Cassid^e, are thick and heavy, the
spire is short, and the aperture terminates in front in a
short recurved canal, the coluraellar lip is covered with a
thick deposit of callus, and, like the other, is toothed or
ribbed. The animal has a large head, a long exfensible
proboscis, and a large foot. These sjjecies are mostly
large and active carnivorous animals, feeding chiefly on
bivalve molluscs. Owing to the fact that the shell is
made up of differently colored layers, the helmet shells
are extensively used in the manufacture of shell cameos.
" Genoa and Rome are the seats of the best work, al-
though many common ones are cut in France. In Rome
there are about eighty shell-cameo cutters, and in Genoa
thirty, some of whom also carve in coral. The art of
cameo cutting was confined to Rome for upwards of forty
years, and to Italy until the last twenty-six years, at which time an Italian began cutting
cameos in Paris, and now over three hundred persons are employed in that city. . . .
The shell is first cut into pieces the size of the required cameos, by means of diamond
dust and the slitting mill, or by a blade of steel [soft iron '?] fed with emery and water.
It is then carefully shaped into a srpiare, oval, or other form on the grindstone, and
the edge finished with the oilstone. It is next cemented to a block of wood, which

Fig. 459. — Aporrltals occidentalls.

Fig. 460. — Cassis glauca, helmet shell.

serves as a handle to be grasped by the artist while tracing out with a pencil the
figure to be cut on the shell. The pencil mark is followed by a sharp point, which
scratches the desired outline, and this again by delicate tools of steel wire, flattened at
the end and hardened, and by files and gravers, for the removal of the superfluous
portions of the white enamel. A common darning-needle, fixed in a wooden handle,
forms a useful tool in this very minute and delicate species of carving. The careful

352

LO WER IN VER TEBRA TES.

manipulation necessary in this work can only be acquired by experience ; the general
sliape must first be wrought out, care being taken to leave every projection rather in
excess, to be gradually reduced as the details and finish of the work are approached."

About fifty species of helmet shells are known, all fropi the warmer seas. Cassis,
the largest genus, has its metropolis in the eastern seas, a few species being found in the
West Indies and in the Mediterranean. The species most used for cameos is the black
helmet, C. madagascarensis, in which the white outer layer covers a darker, almost
black, second layer. The external surface is not, as the common name would appar-
ently imply, wholly black. The whorls are a dirty white, and the outer part of the lips
are rosy, the black being at and near the edges of the aperture. It reaches a lengtli
of nearly a foot. C fflauca, the species figured, is smaller ; it comes from the East
Indies. The other genera of the family are Cassidaria, Oniscia, and Pachyhatron.

1 lo 401 — JJuttum ptiilti tun ahtll

The members of the family Doliid.e are large, with thin shells, the whorls of which
are ventricose, the body whorl Ijeing very large, and ornamented with revolving ribs.
The animal is large, and is provided with a remarkably developed proboscis, which is
long, cylindrical and flexible. The foot is very large and lobed in front; the tentacles
arise from a distinct head, and the eyes are placed on small ]iedicels growing out from
the bases of -the tentacles. In the 3-oung the shell is closed by an operculum, but it
disajipears with growth.

The species of Dolmm are more or less globular, with a very large aperture, and
have received the common name, tun shells, while the species of Ficida are known
from their shape as fig or pear shells. Both genera are tropical or sub-tropical, active
molluscs, living on animal food. The shells are not usually brightly colored, but the
animals themselves are handsomely marked.

Last in the order comes the Teitonidje. In conchological characters it belongs
near the Muricidaa, but in dentition, development etc., its place is here, the lingual

MOLLUSCS. 353

ribbon bearing seven rows of teetli, one rachidian, flanked on either side by three lat-
erals. The shells are ornamented with varices, the character of which serves to dis-
tinguish the two principal genera. In Ranella a varix is formed at
each half turn, so that the shell bears a flattened appearance, due to
the prominent and continuous varices of the whorls ; in Tritoniuin
the varices are not continuous, but are found at irregular intervals.
Almost all of the hundred and fifty species live between the tropics,
where they feed ujion decaying animal matter, the species of Ranella
being among the most prominent of the molluscan scavengers. Tlie
species of both genera are handsomely colored, and some of those of
Tritoniuin are among the largest of gasteropods. The shells are
heavv, but the animals are, nevertheless, very active; some are lit- vig. ^2.— Ranella

,',.,, . . , ' ^ bitubercularis.

toral, while others live in deeper water.

Order VI. — HETEROPODA.

The naturalist, when skimming the surface of the ocean far from land, usually
captures numbers of pelagic forms with bodies as transparent ns glass. When care-
fully studied, these forms are of the greatest interest ; there will be the curious worms
known as /■S'a^/jWa, eel-like fishes {Leptocephalus) whose position is far from certain,
shrimps and larvfe of Crustacea, Salpce, and jelly-fishes. Among the number will
usually be found specimens of the groups of molluscs known as heteropods and
pteropods. With tlie former of these two we have now to deal. The Heteropods
are streptoneurous gasteropods specially organized for a jielagic life, and the modifica-
tions which they have undergone serve to place them as highest in the series. Yet
small as is the group, the variations existing in it are by no means inconsiderable.
The foot has become modified for swimming, and may have three typical divisions
well marked, or it may be reduced to a thin vertical fin, small in proportion to the
body. The body may be developed in the normal manner, and the visceral hump
coiled in a spiral, bearing a shell, or it may be simply cylindrical and the visceral
hump completely atrophied.

The nervous system is constructed on the usual gasteropod type, and, together
with the sense organs, is highly developed. The eyes, two in number, are enclosed in
separate capsules, and are moved by appropriate muscles. They are highly organized,
with cornea, iris, lens, and retina, and, like those of the cephalopods to be described
farther on, they are much like those of vertebrates, the principal difference being in
the relative positions of the fibres of the optic nerve and the layer of rods and cones.
The large ears are placed at or near the sides of the cerebral ganglion, and receive
their nervous supply from it. The organ of smell is also highly developed, and is
placed near the gills when these latter are present, or in a corresponding position
when the branchiag have disappeared. The organ consists of a groove of ciliated sen-
sory epithelium placed just above an olfactory ganglion and innervated in the nonnal
manner.

Owing to the great transparency of the living animals, the study of the internal
structure is an easy task ; no dissection is necessary to ascertain the i)rincipal features,
all that is required being to place the animal under the microscope. The adjoining
figure of the structure of Atlanta was originally made in this way. The head extends
forward, more or less like a proboscis, and bears the eyes and usually a pair of ten-
voL. I.— 23

354

LOWER INVERTEBRATES.

tacles. At its extremity is the large buccal mass, wliich can be protruded so as to
bring the well-developed lingual ribbon, with its sharp and movable teeth, against its

FlQ. 463. — Atlanta peronii ; n, brain; ?), iiifra-oesophagcal ganglia; e, eye; f/, gills; /i, henrt;
/.-, liiclney; /, liver; m, mouth; o, ovary; p, operculum; t, male reproductive gland.

prey. The general positions and relations of the viscera can be seen from our figures,
and need not be described at length. Gills are usually ])resent, but not constantly so,
occasionally individuals of the same species varying in this respect.

The sexes are separate in tlie heteropods. The eggs are usually laid in long
cylindrical cords, which in the case of Firoloides soon break up into short pieces. In
the Atlantidae, on the other hand, the eggs are deposited separately. The young, in
their development, pass through a trochosphere and then a veliger stage.

All of the heteropods are predatory animals, feeding on the numerous forms
around them. In seizing their prey, the buccal mass and lingual ribljon are extended,
and the lateral teeth are bent outwards; then by a muscular movement the curved

Fig. 4C4. — Carinaria,

laterals are closed against each other, forceps-like, and the prey is secured. The ani-
mals are very ravenous, and in their world they play no inconspicuous part in the
reduction of the numbers of other animals. Comparatively few natur:ilists have
studied the habits of these beautiful animals, except those found in the Mediterra-
nean, and we therefore copy, sometimes word for word, the account given by Mr.
Arthur Adams: — Among the pelagic heteropodous molluscs which we found in cross-

MOLLUSCS.

355

ing the South Atlantic Ocean were vast numbers of Atlantce and numerous Carinarice.
They are crepuscular animals like the pteropods, and are furnished with hyaline shells
of the greatest delicacy and beauty. The Atlanta, with an elegant, glassy, spiral,
carinated shell, globose in one species and flattened in another, is quite a sprightly
little mollusc, probing every object within its reach by means of its elongated trunk,
twisting its body about, and swimming in every direction by the lateral movements of
its vertical dilated foot. I have frequently seen them descend to the bottom of the
glass vessel in which they were kept, fix themselves there in the manner of a leech by
their sucking disc, and carefully examine the nature of their prison by protruding the
front portion of their foot in every direction. Almost all pelagic molluscs usually
swim on their backs in a reversed position, and although I have seen them commonly
swim in this way after capture, they frequently progress feebly with the shell upper-
most. When fresh and just taken, I have seen both Atlanta and Carinaria swim
with their bodies in every position ; on their sides, on their backs, and with the foot
downwards. The Carinarice are swift and rapid in theii- movements, and dart for-

h

■ r. n

/I A ^ M

Fig. 465.-

- Pterotrachea scutata; a, shield; h, proboscis; c, mouth; d, float; e, suclcer; g, cloacal sac; h, gills;
/.', genital gland; /, alimentary canal; 771, eye.

wards by a continuous effort, moving their foot and caudal appendage from side to
side as a powerful natatory organ ; they do not progress by sudden jerks like Atlanta.

Three well-marked families of Heteropoda are recognized by naturalists. In the
Atlantid.^ the visceral hump is well developed, and is enclosed in a spiral, glassy
shell, large enough to contain the animal when retracted. The shell starts in a dex-
tral spiral, but soon becomes flattened and bilaterally symmetrical. Its edge is pro-
vided with a sharp keel, and the aperture is closed on the retraction of the animal by
a thin ovate o])erculum. But two genera are known, Atlanta and Oxi/gyrus, contain-
ing a total of al)out twenty-fi\e species, all from the warmer seas. The fossil genus
liellero2')hon possibly belongs here.

In the C.\RiXARiD.t: the visceral humji and the shell ha\e undergone considerable
reduction in size, ns shown by our figure. The shell is liyaline, and from beneath its
margin project the gills. The middle lobe of the foot is alone prominent, and extends
from the lower surface of the body like a vertical fin. The tentacles are well devel-
oped. Tlio two genera Carinaria and Cardlapoda contain a baker's dozen of sjiecies.

In the Pteeotracheid.e the reduction of the visceral hump is carried to its
fullest extent. The animal forms a long, cylindrical body, relieved only by the ven-
tral foot and the small and inconspicuous gills, which are unprotected in some forms,

356

LOWER INVER TEBRA TES.

project but a short distance from the body. The shell is absent, and the foot is pro-
vided only in the male with a sucking disc. Two genera are recognized. In Ptero-
trachea (= Firola) no tentacles are jjresent in either sex, and the tail is pinnate. In
the other genus, Firoloides, tentacles are present in the male, but the tail fin is simple
and slender, and the gills may be present or absent even in the same species. The
egg sti-ing of the Pterotracheans is much like that of Carinaria ; it is long and
subcylindrical, and the eggs are imbedded in a single i-ow in the glassy matrix. Ovi-
position api^ears to take place tlie whole year round, but most abundantly between
September and March. The Pterotrachem seem to possess great vitality and to with-
stand injuries which would be certain death to other forms. The loss of the gills is
of no especial consequence, and indeed they are so small in proportion to the body
that they are of no great use, and are to be regarded as rudiments of respiratory
organs which have been retained during a retrograde development. This vitality
goes even farther, as the following quotation will show: — ''■Anops jjeronii, described
and figured as having no head, was probably a mutilated Firola. ' Such siDecimens
are very common, and seem just as lively as the rest.' "

Sub-Class III. — Pteeopoda.

The wing-footed Mollusca is another group, the position of which is far from
certain. By some it is made a class equivalent to the acephals and cephalopods,
some place it near the base of the cephalophorous series, and one
recent author has regarded it as a member of the Cephalopoda. The
best authorities are, however, inclined for the present to regard it as
a member of the Cephalophora, assigning it a position at the top of
the group, a course which we will adopt.

The pteropods are jielagic molluscs which derive their name from
the fact that portions of the foot (epipodia) are expanded and fitted
for aquatic flight. The body is sometimes long and stretched out in
a straight line ; at others it is coiled in a spiral. The anterior part, or
head, is usually not plainly differentiated from the foot. In some the
mantle is not well marked, and the body is naked ; in others the
mantle is well developed and seci-etes a glassy, horny, cartilaginous,
or even calcareous shell, the two sides of which are almost invariably
alike, and into which the whole body can be retracted. At the an-
terior end is the mouth, which is either surrounded by two tentacles,
or six protrusible processes armed with minute sucking discs, or by
(as in Pneumoclermon) two long arms bearing suckers like those of
a cuttle-fish. The mouth is provided with jaws and a lingual ribbon,
the teeth of which vary between moderate limits, some having twenty-
five, and others as few as three in a transverse row. Salivary glands
are present, and just behind the entrance of their ducts the alimentary
Fig 466 -c»-eseisocic- <''*"=^1 widens into a stomach, and then contracts to form the intestine,
uta: h. brain; h, ^hich, after a number of convolutions, bends on itself, terminatins;

heart; r, reprocluc- ' i > ^

live organ; s, sto- uguallv on the ri"ht side near the edge of the mantle.

mach; w, wings. ■' ^ , , n i -i i i j

The circulatory organs are but poorly de\eloped, and a closed sys-
tem does not exist. The arteries end with wide openings in the body cavity. Here the
blood passes about between the tissues through spaces without proper walls, going to the

A

4.

.■^'"

^zi^M

"-\*-

Pteroirachea ; a heleropod.

MOLLUSCS.

357

resi^iratory organs, and thence to the heart. In some forms no respiratory organs are
present, the skin serving the purpose, but in others gills occur, none of which (except
possibly those of Pneuniodermon) are the homologues of those of most molluscs. In
Pneumodermon the gills are borne on the hinder end of the body, but in the theco-
somatous forms there are folds in the mantle cavity which subserve respii-atory pur-
poses. The kidneys are long, contractile tubes, communicating internally with the peri-
cardial cavity, and externally either with the mantle cavity, or with the exterior. In
nervous system the ptei'ojjods are very similar to the 02)isthobranchs.
The cerebral g.anglia in one group are nearly united and placed above
the throat, but in others they occupy widely separated, lateral posi-
tions. Two auditory capsules are present, placed near the jjedal
ganglia, but eyes are either absent or remain in a very rudimentary
condition, a fact which accords with their nocturnal habits.

The pteropods are hermaphroditic, the genital glands being placed
beneath the heart in the visceral sac, and commonly possessing a
common duct. The eggs are laid in long cylindrical strings, which
float freely about in the sea. The development of some of the species
has been followed by the eminent Swiss embryologist, Hermaim Fol.
The larva is provided with a velum and a shell, the latter capable of
being closed by an operculum. With growth, the embryonic shell
is cast aside, and in some is replaced by a second permanent shell,
while others remain naked through life. This presence or absence
of a shell in the adult is coi-rellated with other structural peculiarities
which served, in the hands of De Blainville, to divide the sub-class into two orders.

The pteropods are mostly small, but few acquiring a length of an inch or more ;
yet, notwithstanding their small size, they are objects of beauty. They live upon the
high seas in all quarters of the globe, at times appearing in vast multitudes, especially
at the approach of darkness and during the later moments of twilight. They swim
about by the violent flappings of their wings, or they retract these organs and sink at
will into the depths of the sea, out of the reach of storms.

Fjg. 4G7. — Cuvieria
coiitmella.

Okdek L — THECOSOMATA.

As the name imjjlies, this division of the pteropods has the body enclosed in a
case or shell, and with this protection of the body are associated other structural
features, which need to be only briefly alluded to. The head is but feebly developed ;
indeed, is frequently not distinct from the rudimentary foot which remains in con-
nection with the wings or greatly developed epipodia. Rudimentary tentacles are
present.

In the Hyaleid^ the shell is horny or calcareous, never spiral, but either nearly
globular or needle-shaped, the two sides being symmetrical, terminating with one or
three sharp points. The cavity of the mantle opens ventrally and contains a horse-
shoe-shaped plaited and ciliated gill. Best known in the family is the genus Hyalea,
or, as it is frequently termed, Cavolina, tlie species of which belong to temperate or
tropical seas. The shell is nearly globular, somewhat flattened above and rounded
below, while the posterior extremity terminates in three points. The aperture is
narrow and is continued by a slit on either side, through which are protruded folds of
the mantle (shown in our figure), the function of which is uncertain. The Syaleoe

358

LOWER INVERTEBRATES.

Fig. 4C8.

swim in a very erratic manner, darting liither and thither with great rapidity, turning
suddenly, and being always on the alert for food. They, like all the rest of the group,

are carnivorous, devouring immense quan-
tities of microscopic animals. The species
of Cleodora swim in a much more leisurely
manner, not turning as abruptly as those
of the former genus. They have a straight,
triangular shell, terminating in a sharp
point behind, and in front with a trian-
gular mouth. In Styliola (or Creseis) the
shell is round and needle-shaped, running to
an acute tip. The sjDecies average about
half an inch in length and have perfectly
transparent, glassy shells, through which all
parts of their internal structure can be dis-

tinctly seen. S. vitrea occurs on the New

^,3^ England coast. Cuvieria is another genus
iiuaicauuicntata. ^•^^^^ ^^^^^^j^^ receive mention. In early

life it is much like Styliola, but with growth it partitions off the
hinder parts of the shell, and the body moves forward and builds a
swollen and more nearly cylindrical shell. The deserted portions r
of the shell soon become broken off, and the result is the truncated
appearance shown in our figure, which illustrates a species common
to the Mediterranean and the tropical Atlantic. I have seen numer-
ous specimens, each about half an inch in length, collected between
the Bermudas and Florida.

Here, in all jirobability, belong the problematical fossils known
as Comdaria or ' cone-in-cone.' They first appear in the Silurian,
and some reach, for ]")teropods, an enormous size, an Australian
species being estimated to have had a length of about sixteen inches.
They have a four-sided shell, with the ajicx partitioned off by nar-
row, closely placed septa, so that the whole resembles a series of
cones, or rather of pyramids, nested within one another. Those
other long and slender fossils, ornamented with rings, and known Tentaculites, should
also be placed here. They occur in Silurian and Devonian rocks.

The LiMACiNiD^ are readily recognized by the spirally-coiled shell, the whorls of
which are sinistral. The mantle is large and opens dorsally. The species are largely
inhabitants of the colder waters, some being found in the Arctic and Antarctic seas.
On our coast a member of the family, Sjnrialis ffoiildii, is not very uncommon in the
evening, both north and south of Cape Cod. i\Ir. Alexander Agassiz kept several in
confinement for a while, and observed that during the day they were quiet, and rarely
left the bottom of the jars in wliich they were confined, but after dark they became
very active and arose to the surface.

The CvMBULiDiE are noticeable for their comparatively large size and the very
peculiar shell which they secrete. In early life, like the rest of the group, they have
a small, spiral, horny shell, but this becomes lost and in its place the animal secretes a
cartilaginous slii)pcr-shaped shell, a])parcntly jiossessing no more consistency than
ordinary gelatine jelly. In this thick, transparent, flexible shell sits the mollusc, like

Fig. 469.— Cleodora
jiijvamiilaia.

MOLLUSCS.

359

tlie old woman in her shoe, pndclling about by the large oval wings ; but, unlike the
other shelled pteropods, it has not the power to retract itself within the aperture.
Two genera are known ; Cyinbulia, with a slipper-shaped shell pointed in front and
square behind, and Tiedemunnia, with a body much like that of CymbuUa, but with
the shell internal. Tiedemannia can change its colors at will by means of chromato-
phores much like those of the cephalopods soon to be described.

Oeder II. — GYMNOSOMATA.

The Gyninosomata are naked pteropods, in which the head is distinct and well
sepai-ated from the body and the foot, and in which well-developed tentacles are
present. The wings are distinct from
the foot, and external gills are present
in one family. Tlie young at first are
provided with a shell and swim by means
of a velum, but soon both these embry-
onic structures are lost, and, pending
the development of the wings, the larva
swims by means of bands of cilia which
surround the body, as shown in our figure
of the larva of Pneumodermon.

In the Clionid^ the body is spindle-
shaped, and the head bears tentacles
which are without suckers. In CUone
there are two of these tentacles, and,
besides, from either side of the mouth
arise three pairs of extensible processes
armed with minute suckers. The num-
ber of these suckers is enormous. In
the fresh specimen the appendages are
reddish in color, but under a low power
of the microscope the color is seen to
be due to a number (about three thou-
sand on each tentacle) of red cylindrical
sheaths, and upon the use of a higher
amplification each of these cylinders is
seen to contain about twenty suckers ]ilaced on slender stems, and capable of being
protruded from the mouth of the sheath. Now^ since a sheath contains twenty
suckers, and since there are about three thousand sheaths on each a)ipendage, a
simple mathematical operation shows us that each Clione is furnished with about
360,000 suckers.

Clione horealis, as its name implies, is an Arctic form which is frequently seen in
vast patches. Together with Limaciiia, horealis, a species belonging to the last order,
it furnishes the principal food supply of the whalebone whales. The whalers call it
'brit,' and the presence of one of these schools of brit is considered as indicative of
a good whaling ground. (JKone papilionacea occasionally occurs on the eastern coasts
of the United States, and has been re]iorted as far south as New York. It may be
that its apparent rarity is due to the facts that it is a northern form, and that natural-

FlG. 470. — L.arva of Pneumodermon,

360 LOWER INVERTEBRATES.

ists are not in the habit of trailing the surface net in the winter. This species reaches
a length of about an inch and a half.

In the Pneumodeemonid^ the body has much the same shape as in the other, but
it is distinguished by the presence of posterior external gills, and two extensible arms
bearing suckers much like tliose of the ceiihalopods. Specimens of P neumodermon
are common in the Mediterranean and in the warmer Atlantic. They swim strongly,
but when touched by a foreign object they roll themselves up like an armadillo, and,
feigning death, sink until out of the reach of apparent danger.

Class III. — CEPHALOPODA.

We have now reached the highest group of the molluscs, the one which embraces
the squids and cuttle-fishes, and which has given rise to many of the tales and legends
of the sea-serpent and other marine monsters. But before indulging in these stories,
we must first look at some of the structural and cmbryological features which mark
off the cephalopods from the rest of the molluscs, a distinction which has always been
recognized, though the reasons therefor have not until recently been scientifically
formulated. This confusion has been due to the fact that the cephalopods are a highly
organized type, which, in course of a long residence on the earth, have eliminated all
traces of a metamorphosis from their development, and which consequently progress
in a straight line from the egg to the adult.

The body of the cephalopods is envelojjed in a mantle, open only at the anterior
end, from whence proceeds the head, separated from the body by a slight constriction
or neck. On either side of the head is a large eye, the structure of which will be
described farther on. Beyond the eyes arii^es a circle of usually eight or ten lobes, or
'arms,' in the centre of which is the mouth. Part of the difticulty in homologizing the
ceph.alopods witli the other gasteropods has arisen in connection with tliese arms.
They were early recognized as corresponding to the foot, and, as they arose from the
head, the name Cephalopoda (head-footed) was applied to the group. At a later date,
the siphon (a structure to be described immediately) was studied, and again the foot
was recognized. Which was right? Further investigation showed that both were
correct. The arms correspond to the anterior division (propodium), the siphon to the
middle one (niesopodium), while the metajjodium is absent, or represented by a rudi-
ment, forming a valve in the siphon of some sjiecies.

The arms, or tentacular lobes, as we have just said, surround the mouth. In the
Nautilus they bear peculiar tentacles, capable of being retracted into tubular sheaths.
In the rest of the cephalopods they are longer, and are armed on one side with spheri-
cal sucking organs, — acetabula, they are called. Each one of these sucking organs
has a rim, which can be closely applied to any foreign body, and the hold increased
by means of numerous fine hooks around the edge. In the centre is a moveable por-
tion, which, from its physiological resemblance to the plunger of a pump, has received
the name of piston. The animal applies these suckers to any foreign object, and then
pulls out the piston. Besides these suckers, certain arms of some species bear numbers
of sharp, recurved hooks. Of the manner of capturing the prey we shall s]icak later.

Mor])hology shows (in a way which need not here be discussed) that these arms
and tentacles correspond to the first division of the foot (propodium) of other mol-
luscs. Next comes the siphon, the homologieal mesopodium. This is a tubular
structure, arising from what is usually called the ventral surface of tlie body, and

MOLLUSCS.

361

projecting a short distance outside tlie mantle. In Naidilus the two lobes of the
siphon are separate, being merely folded one upon the other in order to form the tube,
but in all other living forms this condition is character-
istic of an embryonic stage, and, long before the adult
is reached, the two halves unite.

The shape of the mantle depends on that of the
body. In all it is a cup-shaped or conical envelope, .
attached to the rest of the animal by a narrow line on
the dorsal surface. Its anterior margin is free, but is
pi'ovided with little depressions which fit o^er corre-
sponding cartilages on the sijihon, so th.at the only
communication between the cavity of the mantle and
the exterior may be through the siphon. The mantle
is highly muscular and in life is constantly expanded
and contracted, alternately filling and emptying the
cavity. The water thus taken in subserves the pur-
poses of respiration, and also plays an important part
in locomotion. The animal takes the water in through
the free space between the neck and the mantle, and
then, if using it only for respiratory purposes, passes
it out again in the same way ; but if it desires to
change its position, the mantle is hooked to the
siphonal cartilages, and then the water is forced out
through the siphon. Changes in direction are pro-
vided for by the flexibility of the end of the siphon.
When the animal wishes to go in a backward course,
the siphon is left in its normal condition ; when in a
forward direction, the end of the sijihon is bent over
the edge of the mantle, so that the current is directed
toward the end of the body, and by the reaction loco-
motion is effected.

In all but a very few of the cephalopods, the mantle
secretes a shell, which may be either horny or calcare-
ous. In the young of all, a shell gland .ajipears exactly
as in all other molluscs, but in the great majority of
the living forms it soon becomes enclosed by the in-
growth and coalescence of the edges, and hence the
shell is internal. In this case it is usually much longer
than broad, and serves to give strength and stiffness

to the otherwise soft body. In Spir-
ula an exception is found. The shell
is enclosed in the body, but the gland
which forms it does not become com-
pletely closed. The shell, also, is not
a long flat object, but is tubular and
coiled in a spiral, and, moreover, is
partitioned off and traversed by a slender tube, much like that in the shell of JVcmti-
lus now to be described. In this genus the shell is external, but the early stages

Fig. 471.— External anatomy of Loliqo
pealei, as shown by cutting open the
mantle; a, arms; 6, eye; c, siphon; d,
cartilages of siphon, over which hook
those of the mantle, e; f, free edge of
mantle; </, mantle; A, gills; i, rectum;
m, ink-bag; n, penis; q. intestine; r,
veins from gills; s, gill muscles; (,
branchial artery; h, branchial heart;
t', mantle artery; tt\ posterior venie
cavae; a:, visceral sac; ?/, cavity of
mantle.

Fig. 472. — Section of Spimla australis, shelving the relations of
the shell to the animal.

362

L 0 WER IN VER TEBRA TES.

of its growth have not yet been studied. In the adult it is coiled in a flattened
spiral, like that of a Flunorhis. A very important distinction is, however, to be
noticed in the relations of the shell to the animals in these two forms. In Planorbis
the foot is turned toward the inside of the coils; in Nliutilits the reverse is the case.
The shell, to exactly corresjjond, should be unrolled and coiled in the opposite direction.
Besides this peculiarity the shell of the JVuutilits is chambered. At regular periods
of growth the animal moves forward in its shell, and partitions off a chamber by
means of a calcareous partition ; again and again is the process repeated until the
result is the series of cells so familiar to all in the sawed shell of the pearly nautilus.

A similar partitioning off of the shell is somewhat common among the gasteropods,
and several instances have been mentioned in the preceding pages, but in Nautilus
and its allies a feature is introduced unknown elsewhere in the Mollusca, and, indeed,
in the animal kingdom. In tliese forms the partitions of the chambered shell are
traversed by a cord-like pedicle arising from the central portion of the dorsal region of
the body. This pedicle, in passing through the partitions, foi-ms a more or less tubtdar
series of openings known as the siphuncle, and by this tube any recent or fossil shell
may at once be recognized as belonging to tlie Cephalopoda. The deserted chambers
are filled in the living specimens with a gas, the purpose of which seems to be to lessen
the specific gravity of the animal. The gas is said to be a mixture of oxygen and
nitrogen, the latter in greater proportion than in the atmos])here. How it obtains
entrance to the chanibers is unknown ; possibly it is secreted by the animal, as is the
case in manv other animals. Arcella (one of the Protozoa allied to JDlJflugia) fills its
shell with gas ; the float of the siphonophores acquires its buoyant qualities from the
contained air, while in the vertebrates the gaseous contents of the air-bladder in the
bony fishes will at once suggest itself in this connection.

The mode of .the formation of the chambers and the forward move-
ment of the animal ai'e also obscure. It would, however, appear prob-
able that there is a periodicity in the operations, and it has been
suggested that " each septum shutthig off an air-containing chamber is
formed during a period of quiescence, probably after the reproductive
act, when the visceral mass of the Nautilus may be slightly shrunk, and
gas is secreted from the dorsal integument so as to fill up the space pre-
viously occupied by the animal."

Between the shell of the Nautilus and that of other forms a con-
siderable range occurs, the study of which requires a reference to both
living and fossil forms. A series can be arranged from large shells like
that of the Nautilus, leading down through small and internal but still
chambered forms, like that of Spirula^ and others in which the chambers
still persist, but are strengthened by the addition of external layer.s, as in
the fossil Belemnites; next come forms in which the shell iirojier disap-
pears, and the super-added lamina alone ajijiear {LoK(ju), and, lastly, all
trace of a shell is lost in the adult Octopus. Besides this, another
series may be traced from the closely coiled shell of the Nautilus and
the Ammonites through fossil forms like Crioceras, Auci/loceras, Aiiiso-
ceras, etc., until we reach the perfectly sti-aight shells of the paleozoic
Baculites and Orthoceratites. In the septa of the shells a similar grada-
tion may be seen, reaching from the simple ones of Nautilus and the Orthoceratites to
the highly complicated ones found in the Ammonites. One more shell is all that our

Fig. 473.— ren or
internal sheU of
Loli(jo pallida.

MOLLUSCS.

363

Fig. Hi. — Argommta with shell broken to show the eggs.

space will at present allow us to allude, that of the paper sailor, Argonauta. In this
genus the shell is without connection with the body, but is secreted by two of the
arms, which are greatly expanded for
the purpose, and serves as a nest for the
eggs.

The mouth of the cephalopoda is
armed with a pair of beaks like those of
a parrot, with sharp cutting edges. In
the Nautilus these beaks are calcified,
but in all other living forms they are
horny. Between the jaws is the tongue,
and below them is a lingual ribbon, to
all intents and purposes like that of the
cephalophorous JMoUusca. Behind the
lingual ribbon begins the usually narrow oesophagus, into which one or two pairs of
salivary glands pour their secretions. The oesophngus empties into the stomach,
which is of moderate size, but strong and muscular, and provided with a blind appen-
dage (cEecum), which frequently is larger than the stomach itself. From the stomach
the intestine goes forward in a course nearly parallel to that followed by the oesopha-
gus, and terminates in a median vent on the lower surface of the body just within the
siphon. The liver is large, and opens into the caecum. In the dibranchiate forms
there is an ink-bag, borne near the intestine, and pouring its inky secretions into the
rectum, or into the mantle cavity through an opening near the anus. The ink is brown-
ish or black, and is used to create a cloud in the water when the animal wishes to
escape from some danger. The ink is not readily decomposed ; on the contrary, it is
occasionally found fossil in the rocks along with the remains of tlie animal which pro-
duced it. So well has it been preserved that in one
celebrated instance a naturalist drew the portrait of a
fossil squid with the sepia derived from its fossil, but
not fossilized, ink-bag.

The circulatory system is well developed in all the
cephalopods, especially in the higher groups. The de-
tails would prove dry reading, and so we will merely
mention a few facts. There is only one ventricle, but
the auricles may vary from two to four, in accordance
with the number of gills. On each vein going to the
gills is a pulsating vesicle, the branchial heart. It is
in the problematical appendages to these that the
curious worms, Dicyemida, referred to on a preceding
page, have been found. In some true capillaries are
1^" develo]ied, while in others the arteries terminate in the
lacunar of the body. We have just referred to the ex-
istence of one or two pairs of gills. This character is

FlG.475.— Nervous system of female Xnu- . ^ . , , , . ^ ., , ,

tiius: b, branchial nerve; c, cerebral associatcrl Willi otliers, and IS used in tlie naming and

ganglia; o, olfactory organ; or, oviiluct, , ^ ... ,• .i . ■ -r\'i i • i

p, pedal ganglion; r, visceral ganglion; dehiiitiou 01 the two primary groups, Dibraiicluata and
s, optic neive. Tetrabranchiata. Correllated with this variation in the

number of gills and hearts is one in the kidneys, which are also tw^o or four in number.

It is in these points only that any metamerism of the cephalopods is noticeable.

364

LOWER INVERTEBRATES.

The nervous system is greatly concentrated, the cerebral, pleural, and pedal gang,
lia being placed close together around the throat. True organs of smell have been
found only in the Nautilus, where they occupy the normal position at the bases of the
gills. In this genus, as well as in all others, close by the eyes are the openings to a
pair of pits, which have been supposed to have olfactory functions. The ears are two
in number, and are small pits or vesicles which in the adult become entirely shut off
from the exterior. They are placed in the sides of the head below the eyes, and each
contains a single otolith.

In the Nautilus the eye has not reached that high development found in the squids
and cuttle-fish, but in fact it is extremely simple. On either
side of the head are two prominences which contain the eyes.
In the centre of each is a minute hole communicating with a
large internal chamber filled with sea-water. The inner wall
of this is lined by the retina, in %\'hich tlie nerves terminate.
As will be seen, this eye is extremely simple. There is no
lens, no cornea ; nothing but the features enumerated. All
are familiar with the fact that a lens is not necessary for the
production of an image. If we admit the light to a darkened
room, by means of a very small hole, so as to prevent any superimposition of images, a
picture of external objects can be thrown on a screen. This is the physiology of the
eye of the Nautilus. In the Dibr.anehiata the visual organ is very complex, and it is
to be noticed that in its development it passes through a stage closely similar to
that which persists through life in the Nautilus. With development it goes farther,

Fig. 476. — Di.igiam of the eye
of Nautilus ; c, cavity; f.
integument; n, nerves; r,
retina.

Fig. 477. — Section tlirough the head of a young Lolli/o to show the structure of tlie eyes; c. ceso-
phagus; </, c, pedal ganglion; ;/, optic ganglion; /i, ganglionic layer of retina; i, layer of rods;
I:, posterior chamber of the eye; /, lens; m, anterior chamber; o, cornea; p, iris.

and the result is an optical organ which presents some startling analogies to that
found in the vertebrates. When carefully studied it is seen that this resemblance is
superficial, and that fundamentally the two are entirely different. In botli the eye
is provided with a cornea, then comes an iris with a circular pupil, and next a lens
dividing the cavity into two cbambors. Hoi-e, however, the correspondence stops.
In the squid tlie posterior lining of the inner chamber is the retina, with its rods and
cones, and then comes the ganglionic layer. In the vertebrates the relations of these
two are reversed. Embryology reinforces these differences, and shows that the eye of
the cephalopod is greatly different in its development from that of the vertebrate.

MOLLUSCS.

365

■.. ,.■,*..■■

Fig. 478. — Cliromato-
phore of squid, ex-
panded and con-
tracted; enlarged.

Among the peculiar featiu-es of the cephalopods should be mentioned the chroni-
atophores, by which the animal is enabled to change its color quickly. Such structures
are found elsewhere iu the animal kingdom, but here they attain
the greatest development. They are best studied in the young-
just after hatching, as then the whole animal can be placed under
the microscojDe and examined with comparatively high powers.
Each ehromatophore is in reality a cell filled with pigment, and
expanded by suitable muscles attached to its wall. These cells
are placed just beneath the epidermis, and, when expanded, the
contiguous ones nearly touch, so that the auimal appears of a uniform tint. When
the ehromatophore contracts, as it does by its own elasticity, the color is condensed
so that it appears as a very minute black dot, and then the translucent, almost
transparent, character of the tissues is seen. The expansion and contractions of
the ehromatopliores take place with considerable rapidity, so that the changes in
color are remarkable. There are several sets of these chromatophores, each dis-
tinguished by its color, yellow, red, blue, or brown ; and each set expands independ-
ently of the others, so that an animal almost transparent will suddenly turn bright red,
instantly change to a blue, and then a yellow or a brown, or back to its previous colorless
condition. The chromatophores in different parts of the body are also independent,
and sometimes the fins will be bright blue and the anterior part of the mantle an
equally vivid red. When examined under the microscope the whole of these changes
can be carefully studied, and then it is found that the chromatophores are suddenly
expanded, but that their contraction is accomplished in a more leisurely manner.
When expanded they have a diameter of about a fiftieth of an inch, but when reduced
to their smallest size they measure but one two hundred and fiftieth of an inch. The
purpose of this change of color is protective ; and as by it the animal can assimilate its
color to any surroundings, it can readily escape observation by any fishes on which it
may wish to feed or which might otherwise feed on it. In the Nautilus these chro-
matophores do not appear to be present, though they exist in all other forms. With
this capacity for change it will readily be seen that color is a character of no impor-
tance in discriminating the species of cephalopods.

The sexes of the cephalopods are separate. Of the internal
reproductive organs we need say nothing, but in connection
with the reproductive act there are some very interesting fea-
tures. Many years ago Cuvier in dissecting a female Para-
sira, found attached to it a peculiar worm-like object furnished
with numerous suckers. He regarded it as a parasite, and gave
to it the name Hectocotylus. At about the same time the
Italian naturalist Delle Chiaje found a similar structure in
ArgonmUa, which he called Trichocephalus. Several years
elajised before the true nature of these structures was recog-
nized. It was then discovered that this supposed parasitic
worm was in reality one of the arms of the male, which sep-
arates and serves to convey the male reproductive element
to the female. This ' hectocotylization' reaches its highest development in the two
genera named above. In these, one of the third pair of arms (right or left, according
to the genus) becomes thus modified. Just before the period of reproduction, this
arm appears as a nearly globular sac. This then bursts, and from it issues an arm

Fig. 479.— Hectocotylized arm
of Anionaiita after separa-
tion from the male.

366

L 0 WER IN VER TERRA TES.

lai-ger than the rest, which tlie male then charges with one of the packets of sper-
matozoa soon to be described. During the coitus this arm becomes detached and

Fig. 480. — Hectocotylization in the male Argcmauia; in A is shown the sac which iu B has burst
open, allowing the hectocotylized arm to extend itself.

remains adherent to the female, which then swims away. A new arm is formed in

the male before the return of the breeding season.

This subject of hectocotylization has been studied by Steenstrup, a Danish nat-
uralist, who finds that the arm or extent of modification is
variable in the different genera, but in some (among which is
Ommastrephes, so common on our coast) this process has not
been observed. We have just alluded to the
packets of spermatozoa. These are called
spermatophores and are found variously mod-
ified in different invertebrates. In Loligo, one
of the squids which we select as a type, it con-
sists of a slender capsule about half an inch in
length, two thirds of which is occupied by the
spermatozoa, while the remainder contains a
complicated discharging apparatus. On con-
tact with the salt water the sheath ruptures
at one end, and forth issues the discharging
apparatus, dragging tlie spermatozoa after it.
The eggs of the cephalopods are usually
io/ir/o ,■ rt, sTie.aih; 6%acket envcloped in capsules, some of which contain

of spermatozoa; c, discharg- ^ ^ .

ing apparivtus; d, a single as maiiv as two himdrcd ectgs. Tins IS not

spermatozoan. " , \'' ^ ., ,

the case with all, for the writer once dredged
the eggs of an unlcnown cephalo]iod (? Jiossia) which were scjiaiate
and deposited free ujion the ocean's bottom. They were about the
size of a small pea. The shape and size of the capsules vary consider- ^'"aieoFL^fyof'^
ably. Those most commonly found on the New England coasts arc
those of Lolifjo pealei. They are finger-shaped and gelatinous, and so transparent
that the embryos can be readily seen. Usually from twenty-five to a hundred of these

Fio. 4S1. — Spermatophore of

©^

^■-

MOLLUSCS.

367

capsules are miited in a buncli, but I have seen one mass of the eggs of this species
which would more than fill a bushel basket. Owing to the great amount of food-yolk
present, the eggs of all cephalopods are very large, and the develojjment is extensively
modified from the same reason.

Tlie development of but few of the cephalopods has been studied, and all that is
known throws but little light on the relationships of the group. A knowledge of the
development of JVauiilas is a great desideratum. The follow-
ing account relates largely to Loli(jo peaUi, the only species
studied by the writer. Owing to the great quantity of food
yolk and its distribution, the segmentation of the egg is at first
confined to one pole, and the result is that the first stages of the
blastoderm are very like those in the chick. The blastoderm
gradually increases until it envelopes the whole yolk, but before
that stage is reached some of the organs begin to be outlined.
First to appear are a shallow pit, the shell gland, at the extrem-
ity of the body, and two others closely similar, the rudiments
of the eyes, on the sides of the body. Then a fold arises, the
first traces of the mantle. The two siphonal folds next appeal-,
and as develo2:)ment progresses they take the form of two dis-
tinct flaps, a condition which is permanent in Nautilus., and
tiien the edges fuse together. The first appearance of the arms
is in the shape of simple prominences.
At this time the yolk extends as a huge
mass from between the arms, but, as
growth continues, it is gradually absorbed and transformed
into food for the rapidly increasing tissues. Thus the devel-
opment is direct, and not a trace of a metamorphosis appears.
Even the veliger and trochosphere conditions are lost. The
reasons for this are to be found in the very long history of the
group, together with the high point to which they have attained.
In their structure they are, as we have seen, the highest of the
Mollusca, and hence the transition from the egg to the adult is
very extensive. On this account there is a tendency to drop
all useless and larval features, and to pursue the shortest
course. This tendency exists everywhere in the animal king-
dom, but of course it requires time to eliminate them all.
Time the cephalopods have had. In the lower Silurian rocks,
fossil forms not generically distinguishable from living Nau-
tili are found, and the tetrabranchs flourished in palieozoic
time, while forms assigned to the dibrauchs first appeared in the triassic strata.

Fig. 483. — \'entr,al view of a
rather early embryo of Jjol-
it/o; a, arm's; e, eye; f/, gill;
A, car; }r?, mantle; s. sipho-
nal folds not yet united;
V, vent; I/, yolk sac.

Fig. 4S4. — Einhryo squid in
which the si phon;il folds (.s)
have united, and the suck-
ers or acetabula are ai>-
pearing upon two pairs of
the arms; a. arms; f, eye;
/, tin ; /i, ear; i\ vent.

Sub-Class I. — Teteabranchiata.

We have incidentally alluded in the preceding pages to some of the characters
which serve to separate the cephalopods into two groups, the names of which have
reference to the number of gills. The lower of the two, the Tetrabranchiata, are
represented by but a single living genus. Nautilus, and from that we have to derive
all our knowledge of the soft and perishable portions. These characters may be

368

LOWER INVERTEBRATES.

briefly enumerated as follows : The two siphonal folds are never united ; the tentacles
are numerous and never bear suckers ; the gills are four in number, and, corresponding

to them, four auricles are present ; the renal organs
are also in two pairs, and branchial hearts do not
exist. The character of the eye has already been
described. The shell is either straight or curved,
never internal, and is divided into a series of cham-
bers. Two well-marked families exist, but lately
they have been broken up into a large number of
groujDS, to which family rank has been accorded, but
with these we need not concern ourselves.

In the Nautilid^, the partitions forming the
ihambers of the shell are simple, and concave on
the outer surface ; the siphuncle occupies a nearly
central position ; the aperture is simjile, and the
Fig. 485. - u,uier ..nriaoe of a part of a Nau- external surfacc is nearly or entirely smooth. Over
vintfo^OTidlct's! ''^'''''' ^*^ ^"'^ ^"''' "' ^"^^ thousand species have been described, of which

only six are living at the present time, all belong-
ing to the genus JVautilus, in which the whorls of shell are few, but closely coiled
in a flat spiral. The shells are very common, but the animals are rarely seen ;
this may partly be due to the habits, but more from the fact that the natives of
the South Seas eat the animal when obtained, but use the shell for barter. These
shells are composed of two layers, the outer one being dull and opaque, but the inner
one is pearly, whence all the sjjecies derive the common name pearly nautilus. Speci-
mens converted into cameos by removing parts of the outer layer by means of acid
are very common, some being really artistic ; this point, of course, depending entirely
on the skill of the artist. The Nautili live in comparatively shallow water, where
they creep slowly over the bottom, or swim by means of the water forced out of the
siphon. They live on animal matter, and the trajis in which they are caught are
baited with crabs, sea-urchins, and the like.

Of the many fossil genera we need say but little. They occur in all the rocks from
the lower Silurian to the present time. In
shape, all transitions may I)e found, from the
perfectly straight Orthoceras to flat spirals like
Nautilus, and cunical spirals like Trochoceras.
Some of the species of
the former genus grew
to an enormous size,
and Prof. J. S. Newber
tita7i weighed some tons.

In the Ammonitid^ the septa are lobed or folded at their
margins, so that the line of their insertion into the shell fre-
quently has a bushy or dendritic appearance. Associated with
the Ammonites frequently occur horny or shelly plates called
aptychi or anaptychi, the relations and functions of which are
entirely problematical. None of the family are now living,
and but a few extended into the tertiaries. The bulk of the species belonged to the
mesozoic rocks. In form they vary almost exactly as do the members of the last

Fig. 486. — Anci/loceras.

vy estimates that the fossil Orthoceras

Fig. im.—.-lmvwnite.

MOLLUSCS. 369

family, loosely coiled and straight forms being common. One of the most interesting
of modem investigations was that conducted by Professor Alpheus Hyatt on the em-
bryology of these extinct forms. Every specimen contains in its interior the shell pos-
sessed by the embryo, and by breaking open the fossil this ca.xi be examined and studied.
In this way, by studying large collections, Professor Hyatt arrived at a clear idea of
the development of the group, and consequently of the manner in which the numerous
genera should be arranged in order to exhibit their affinities.

Sub-Class II. — Dibkanchiata.

In its characters this group differs considerably from the last. As the name
implies, but one ])air of gills are ])resent, and as a consequence but one pair of auricles
exists The circulation, however, is reinforced by a jjair of contractile organs
(branchial hearts they are called) on the vessels which convey the blood from all
parts of the body to the heart. A pair of kidneys are present. The folds of the
siphon are united to form a complete tube ; and the arms which surround the head
are furnished with sucking cups. The shell, when i)resent, is internal, and may be
either calcareous or horny ; among those with horny shells, it takes the shape of a flat
plate or a long style, while in others it may be chambered or flat. An ink bag is
always present. This is the group which contains the forms commonly known as
squid, cuttle-fish, kraken, j)0ul])e, and the like, and embraces some of the largest
animals now living, as well as numerous smaller forms. Thanks to the labors of Prof.
A. E. Verrill, the species found on the northeastern coasts of America ai-e as well
known as those from any part of the world. The number of arms is made the basis
of division into two orders.

Oedee I. — OCTOPODA.

In this division the arms which surround the mouth are eight in number, and are
covered with sessile suckers in which the horny lip is absent ; the eyes are small, and
can be covered by the skin, which closes over from all sides ; the body is short and
nearly spherical, and lacks either internal or external shell, and usually also the fins so
characteristic of most of the decajiodous forms ; the mantle is without cartilage, and on
the dorsal surface is united to the head by a broad band. The siphon is without valves,
and the oviducts are paired in all except Cirrhoteutltis, where the right one is aborted.

In the CiRRiiOTEUTHiD.E a peculiar modification of the arms occurs ; they are united
nearly to their tips by a thin membrane, so that the whole coi'responds to an umbrella,
the eight arms answering to the ribs, while the rather long body bears a fin on either
side. The genera are Cirrhoteuthis and Stauroteuthis, and the known species come
from the northern seas. Of the latter genus but a single specimen is known ; it is
called S. Sj/rtensis, and was taken about thirty miles east of Sable Island, Nova Scotia.
Cirrhoteuthis tniilleri is found in the Greenland seas.

The next family, the Piiilonexidje, has no fins ; the mantle has an apparatus where-
with it may be locked to the siphon ; the arms are united to a greater or less extent by
a membrane, and the dorsal ones are most developed; there are several pores in the
surface of the head which commimicate with aquiferous cavities. In this family hecto-
cotylization reaches its greatest extent, the third arm of the right or left {Argonauta)
side being thus modified. The animals swim well.
VOL. I. —24

370

LOWER INVERTEBRATES.

The species known as Parasira catenulata occurs on both sides of the Atlantic,
specimens being most numerous in the West Indies and the Mediterranean. A few
years ago a single specimen was found on the southern New England coast. Two
species of the genus have been described, but, according to Stcenstrup, the differences
are sexual, the form known as P. carena being the male. The flesh of tliis species is
tough and unwholesome. Tlie ventral surface of the body is ornamented by tubercles
and reticulating ridges. Closely allied is the genus to which Professor Yerrill lias
applied the name Alloposus, but whicli at tlie same time presents resemblances to the
last family in the membrane which unites the arms for about two thirds their length.
Large female specimens of the oidy species {A. mollis) weigh over twenty pounds, and
have a total length of thirty-two inches.

The only other genus of the family which we need to mention is Argonauta, the
one which embraces the paper sailors, so well known for the delicate and beautiful
shell which they secrete. This sliell, however, is not homologous with that of other

molluscs, as is seen by the method
of its formation. In the female the
two dorsal arms are expanded into
two broad membranes at their ex-
tremities, and it is these two mem-
branes that secrete the shell. The
purpose of the shell is merelj' to
protect the eggs, and, although the
female sits in it, she has no organic
connection with it. Tliis fact, taken
with the finding of female paper
sailoi-s without shells, led to many
a dispute among the older natural-
ists, and for a long time it was
maintained that Argonauta took
the shell of some other animal. These delicate egg-nests, which are produced by the
females alone, are frequently washed ashore in tropical countries in large quantities.
On our shores they are rare, only two with the animal having been reported, though
about a dozen dead shells have been dredged by the U. S. Fish Commission a hundred
miles south of the New England coast.

The paper sailor is often described at the present day as taking advantage of fine
weather and coming to the surface, when it lifts its broad .arms and sails away before
the breeze. It does nothing of the kind ; it swims, as do all other cephalopods, by
forcing water through its siphon, its broad arms clasping the shell and the others trail-
ing behind. The Argonautce, of which nine species have been described, are all pelagic,
coming to the sui-face at the spawning season, and sinking to the bottom at other
times. The male is but about an inch in length, being sometimes scarce a tenth of the
size of the female.

The OcTOPODiD^ are more littoral than the last family, and have the mantle con-
nected to the visceral sac by muscular bands, while there are no :tquiferous pores in
the head ; the arms are long and more or less webbed, and are furnished with one,
two, or tliree rows of acetabula, and lateral fins niay be present or absent.

First in order comes the Octopus of science, the subject of many a weird and blood-
curdling tale. Most promitient among these is that description of the devil-fish given

Fig. 488.

- Shell or egg-nest of Argonauta argo, the paper sailor.

MOLLUSCS.

371

f"^ f ^\

by Victor Hugo in his " Toilers of the Sea " ; but, after so many have shown the falsity
of this creation, it is only necessary to briefly refer to the wonderful composite. The
French name for these animals (poulpe) is but little different from the term polyp ; an
encyclopedia was consulted for both words, and the information obtained combined, and
then, for a name, the term Cephaloptera (the true devil-tish, one of the rays) was stolen,
and the whole set forth in the most vigorous language; a description of the appearance
and habits of an animal which never existed, and which never will. The Octopi some-
times reach a large size, 0. vuglaris of the West Indies and tlie Mediterranean reaching
a length of nine feet and a weight of sixty-eight pounds, while the 0. punctatus of our
Pacific coast " reaches a length of sixteen feet, or a radial spread of nearly twenty-eight
feet," the body in such a sj)ecimen being about six inches in diameter and a foot in length.
There is no satisfactory evidence that any species of Octopus has ever intentionally at-
tacked a human being, or that any one has been seriously injured by them. In habits
they are timorous, hiding among rocks and feeding on crabs and molluscs. In tlieir
nests will frequently be found bushels of clam shells, which tell the tale of their feasts.

Some fifty species of this genus liave been described from the whole world, and
within the past few years sev-
eral have been ascertained to ^^j'^-^ o-f^^<-
exist on or near the New Eng-
land shores ; but of these, with
the exception of 0. bairdii, a
widely distributed form, speci-
mens are as yet rare. The
characters which separate Oc-
topus from the other genera of
the family are a small rounded
body without fins, two rows of
sessile suckers on each of the
long and slender ai-ms ; the
right arm of the third pair is
hectocotylized in the male.

The best known species is
O. vulgaris, which lias often
been studied by European nat-
uralists, and which i)lays an
important part in the food
supjjly of tlie countries around
the Mediterranean. They are
eaten especially during Lent,
the traditions and decisions of
the mother church not recog-
nizing their meat as flesh, but
rather as fish.

Professor Verrill thus de-
scribes the habits of our Octopus bairdii, specimens of which he kept in confinement
for several days. "When at rest it remained at tlie bottom of the vessel, adhering
firmly by some of the basal suckers of its arms, while the outer portions of the arms
were curled back in various positions ; the body was held in a nearly horizontal posi-

FiG. 489. — Dorsal and side views of Octopus bairdii ; the upper figure
shows on the right side an hectocotylized arm.

372 LOWER INVERTEBRATES.

tioii, and the eyes were usually half closed and had a sleepy look. . . . When dis-
turbed, or in any way excited, the eyes opened more widely, especially at night ; the
small tubercles over its surface, and the larger ones above the eyes, were erected,
giving it a decided appearance of excitement and watchfulness.

" It was rarely, if ever, observed actually to creep about by means of its ai-ms and
suckers, but it would swim readily and actively, circling around the pan or jar, in
which it was kept, many times before resting again. In swimming backward, the par-
tial web connecting the arms together was used as an organ of locomotion, as well as
the siphon ; the web and the arms were alternately spread and closed, the closing being
done energetically and coincidently with the ejection of the water from the siphon;
and the arms, after each contraction, were all held pointing forward in a compact
bundle, so as to afford the least resistance to the motion. As soon as the motion re-
sulting from each impulse began to diminish sensibly the arms were again spread and
the same actions repeated. This action of the web and arms recalled that of the disc
of the jelly-fishes but it was more energetic.

"The siphon was bent in differeiit directions to alter the direction of the motions,
and, by bending it to the right or left side, backward motions in oblique or circular di-
rections were given, but it was often bent directly downward and curved backward, so
that the jet of water from it served to propel the animal directly forward. This, so
far as observed, was its only mode of moving forward. The same mode of swimming
forward has previously been observed in cuttle-fishes (Sejjia) and in squids (Loliffo)."
It was much more active in the night, and in freedom is probably nocturnal. In cap-
tivity they could not be induced to touch food.

One species of Eledone (a genus in which the arms bear but a single row of suckers)
is found in our waters, but of this but two specimens have as yet been found.
Professor Verrill has called it E. verrucosa, in allusion to its warty appearance. In
the European seas three species are found, one of which is named E. moschata, in al-
lusion to its musky odor, which, however, is shared by some other cephalojaods. In
confinement, this species, when tranquil, is yellowish in color, and holds itself in much
the same position as that described for Octopus hairdii, but a slight touch is all that is
necessary to excite and enrage it. Then the color becomes a fine maroon, the tuber-
cles on the body become prominent and the expansions and contractions of the mantle
are very irregular; in short, the animal shows every appearance of anger. When
swimming, which it accomplishes in much the same way as does Octopus, the body
takes on another shade of yellow ornamented by bright spots of red ; and when walk-
ing about by means of its arms and suckers, still another hue is seen.

Eledone moschata, as well as other species of the genus, is used as food, notwith-
standing its musky taste and odor, which jiersists after death. Its flesh is more tender
than that of Octopus, and is eaten boiled, fried, or in salads. This species frequents
water usually from ten to twenty fathoms in depth, and in its capture the same methods
are employed as in taking Octojn; earthen jars are lowered to the bottom, and, for
some reason as yet unexplained, these animals soon esconce themselves inside. In a
few hours the jars are pulled up and the prey taken.

Order II. — DECACERA.

The name usually applied to this division (Decapoda) is rather unfortunate, since
it has also been used to indicate the group of Crustacea which contains the shrimps,

Eledoue moschata, musk poulpe.

MOLLUSCS.

373

lobsters, and crabs. For this reason the name Decacera has been substituted. Both
terms have reference to the number of divisions of the foot which surround the head,
the ten arms of this order contrasting strongly with the eight found in the last.
Besides this, there are other characters to be enumerated. The body is usually long,
and comes to an acute point behind, and bears on either side a fin and is strengthened
internally by a horny ' pen ' or a calcareous ' bone.' Tlie two extra arms arise between
the third and fourth pairs of the Octopods, and usually differ considerably from the
others. They are usually longer and more slender, and have the basal
portion narrower than the apex. This slender portion is without
suckers, but the distal portions bear these organs, which, like those of
the other arms, are supported on short stalks or peduncles. These
long arms are usually called tentacles or tentacular arms.

Among the fossil forms referred to this order, is the family known
as Belemxitidje, the exact relationships of which are even yet uncer-
tain. Different authorities have attempted to restore the animal, and
one of these restorations, that of Quenstedt, is shown in the adjacent
figure. Between these various restorations considerable differences
exist. From cei-tain well-preserved fossils it is known that the arms
were furnished with hooks. The shell, however, is better preserved.
It consists of a pen much like that of existing forms, but to this is added
a calcareous chambered shell, the phragmocone, the partitions of which
are traversed by a siphunclc. The apex of this phragmocone is envel-
oped in a second calcareous shell, the rostrum or guard. These fossils,
which are very abundant in some parts of the Jurassic and cretaceous
rocks, have received a large number of popular names, indicative of
their general shape or of the superstitions and myths ^\hich have been
associated with them. Among these may be mentioned arrowheads,
thunder-bolts, petrified fingers, spectre candles, etc. In the outer
chamber of the phragmocone of some specimens the remains of the ink
sac have been found. Some of these fossils are very large, indicating an animal
several feet in length.

As we have just said, the position and structure of the Belemnites are very uncer-
tain. In some respects they seem to be related to Sjnrula ; in others, to forms like
Onitnastrephes. Several attempts have been made to divide the living species of the
order into sub-ordinal groups, the divisions being based upon the calcareous or horny
nature of the shell, or upon the perforate or entire condition of the cornea, but with
all considerable fault can be found, and the result is a highly artificial arrangement.
Of all the families the Spirulid.e seems the most nearly related to the tetrabran-
chiates as well as to the Belemnites, and hence it is well to consider
it first. The chambered shell of Spirula at once suggests that of JVa?«-
tilus (the only other living genus in which it is present) but, as was first
pointed out by Owen, the relationship of the body to the shell is diamet^
rically opposite in the two ; in Mmtihts the ventral wall of the shell
describes a convex curve ; in Spirula the reverse is the case. Another
important distinction exists in the fact that in the former the shell is
external, in the latter internal ; indeed, it seems to represent the phrag-
mocone of the Belemnite, the guard and pen being absent, and the resemblance is
strengthened by an examination of the remains of the genus Spirulirostra. In Spinda

Fig. 490. — Restor-
ation of Belem-
nite.

Fig. 4'JI. — Spl
rula permiii.

374 LOWER INVERTEBRATES.

the eye has an imperforate cornea, ten arms (one pair tentacular) which in the female
bear six rows of minute suckers, but none in the male. The body is oblong, with
minute terminal fins; the female has an oviduct on the right side, and two nidamental
glands ; in the male no hectocotylus is formed. iSjnrida is the only genus.

Although on some shores the dead shells are washed up by thousands, the animals
are among the greatest rarities in the animal kingdom. Only three perfect, and a few
mutilated specimens have as yet been found. Our knowledge of the anatomy is al-
most wholly due to Owen, whose papers on the subject are models in the line of re-
search with very limited material. The shells of Sjylrula fragilis are occasionally cast
up on the outer shores of Nantucket, while a living specimen was dredged by tlie U.
S. coast survey in the West Indies in 1878. It came from a depth of nine hundred
and fifty fathoms. Spirilla peronii and S. australis come from the Indo-Pacific and
Australian seas.

The family Sepiace embraces the true cuttle-fishes, in which the internal shell is
calcareous, the cornea imperforate, the body oval, with long fins, the tentacular arms
very long, and capable of being completely retracted into pouches at the base ; in the
male, the left arm of the fourth pair is hectocotylized. The only genus, Se2na, is the
one which furnishes the cuttle-bone which is found thrust between the bars of every
canary cage, and whose ink is the basis of the pigment sepia. This is still manu-
factured in Rome. The cuttle-fishes are essentially littoral animals and are extensively
caught, not only for the ink and the bone, but for the sake of the flesh, which is used
as food.

The animals, when undisturbed, swim rather slowly and gracefuljy by means of
undulations of their fins, but when startled or alarmed, the siphon and the arms are
worked as in the case of Octopus., and then the fins are wrajjped tightly around the
body. They lay their eggs in black egg-shaped or pyriform capsules attached to sub-
merged objects. They feed upon fishes, crabs, and molluscs. As in all cejihalopods,
the colors are changeable, but in Sepia officinalis zebra-like bands of blackish brown
cross the body.

With the family Loliginid^ we take up some of the squids in which the body is
more or less conical, tapering to a point behind. The fins are large, sometimes extend-
ing the whole length of the body. The cornea is entire, the eyes without lids, the
tentacular arms but partially retractile and distally furnished with four rows of
suckers, while on the other arms there are but two rows. The fourth arm on the left
side is hectocotylized at the tip. The pen is long, slender, and flattened. Three living
genera are known, only one of which, Loligo, is represented on our coasts ; Sepioteu-
thus occurs in the West Indies, and Loliohis in the Pacific. Loligo pealei is the com-
mon squid south of Cape Cod ; it extends south to the Carolinas, but north of the
Cape it is not so common as Ommastrephes illicebrosa. A second species, L. brevis,
extends from Virginia to Brazil, while L. galei occurs in the Gulf of Mexico. The
anatomy, habits, and external development of the former species are pretty well
known. They lay their eggs during the warmer months of the year, in large bunches
of gelatinous capsules which are usually attached to some algae. The young develop
rather rapidly, and at certain times are taken in large numbers in the surface net.
They are eagerly eaten, not only by fishes, but by the larger individuals of their own
species. None of the squid are- used in America as food, but innnense numbers are
caught and used as bait by the fishermen.

Tlie Sepioudjs are closely related to the last family, but differ in having a short.

Sepia officinalis, cuttle llsh; a, male; h, female; c, cuttle-bone.

MOLLUSCS. 375

thick body, rounded behind, the eyes with a lower and sometimes an upi>er lid, the
tentacles more or less completely retractile, and the arms furnished with two rows of
acetabula. The fins are separate, and attached near the middle of the body. This
family is represented on our coasts by tlie genera Sepiola, liossia, and Heteroteuthis,
the species of which are far from conmion.

. The species of Cranchia, the only genus of the family Cranchiid^, have a sliort,
round body, with two small fins on the hinder end a small head, with large eyes, the
cornea of which is perforated so that the sea-water penetrates to the lens, two rows of
suckers on the arms, the tentacles long and armed with eight rows of acetabula.
Closely allied is the family Desmoteuthid.e, with its two genera, Desmoteuthis and
Tao7vius, in which the body is longer and pointed posteriorly.

In the LoLiGOPSiD^ the form is longer and the fins are large, the head very small,
the arms with two rows of suckers, the tentacles not retractile, the sijihou without
valves. Of Ilistioteuthis three species are known, two of which are found in the
Mediterranean, while of the third, H. collinsii, found off Nova Scotia, one imperfect
specimen and the beaks of two others are all that have been found. The other pro-
minent genera are LoUgopsis^ Mastigoteutlds, Chiroteuthis, and Thysanoteuthis.

In the family Teuthidjs the tentacular arms are distally armed with sharp, liorny
and recurved hooks, which, to a greater or less extent replace the sucking discs, and in
some of the genera the other arms bear hooks as well as suckers, while others have hooks
alone. The tentacular arms, which are used, as in all decacerous cephalopods, for the
capture of the jjrey, can be fastened together by the sucking discs for a greater or less
propoi'tion of their length, leaving the extremities to form a living forceps, from which
escape is next to impossiVile. The eyes are provided with lids, and the cornea is per-
forated as in the last family.

Possibly to be placed here is the large species Moroteuthis robusta, found by Mr.
Dall in Alaska. Three mutilated specimens were seen, the largest of which, when
found, had a total length of fourteen feet, but the terminal portions of the tentacular
arms were gone, and so the actual size was someVhat greater. The length of the man-
tle was seven feet seven and a half inches, and the diameter of the body eighteen inches.
A peculiarity exists in the pen, the posterior end of which " is one-sided, funnel-
shaped close to the tip," and "inserted into along, I'ound, thick, firm, cartilaginous
cone, which tapers to a point posteriorly,'' which thus, as jiointed out by Professor
Verrill, corresponds to the guard of the extinct Belemnites, both in position and in its
relation to the pen. Nothing like this is known in any other recent genus.

Among the undoubted members of the family may be mentioned the genus Ony-
choteuthls, in which the forceps of the tentacular arms is well developed. The club
which terminates each of these arms bears on its inner surface two rows of recurved
hooks, while just below are a number of suckers which serve to unite the two arms.
The sessile arms have suckers only. 0. bcmksii, one of the ten known species, ranges
from the Arctic seas to the Cajie of Good Hojie and the Indian Ocean. It is solitary
in its habits, frequenting the open seas, and is most numerous round the banks of gulf
weed. In Mioploteuthis and three or fotir other genera, all the sessile arms bear
hooks but no suckers, the tentacular arms being much as in the last genus.

The last family to be mentioned is the OMMASTEEPHiDyE, in which the body is
long and tapers to a point behind ; the arms are short and without hooks, but fur-
nished with two rows of suckers ; the tentacular arms are not retractile, but terminate
in an expanded club, armed with four rows of suckers. The eyes are provided with

376 LOWER INVERTEBRATES.

lids, and the cornea is perforated so that the salt water bathes the lens ; the siphon is
held by four bands and contains an internal valve (probably the homologue of tlie
inesopodiuni).

The typical genus is Ommastrephes, of which one species, 0. illecibrosus, is the
most common squid north of Cape Cod, though further soutli it is less common, and
rejjlaced by Loligo pealei. From an economic point of view it is a very important
species, for its distribution is coincident with that of the cod-fishery, in which it is
used as bait. They swim in large schools, and are frequently found following schools
of young mackerel and herring, on which they feed. They usually swim backwards,
with the ease and grace of a trout, and a school of them furnishes a beautiful sight,
their color changing instantly to accord with the bottom over which they pass. They
are largely nocturnal, though they are seen in large numbers in the daytime. In the
morning, on Cape Ann, the flats will sometimes be found covered by specimens left by
the retreating tide during the night. When stranded they can do but little to helj)
themselves. Their usual recourse is to begin to pumji water tlirough the siphon, but this
forces them farther on the beach as frequently as it aids them in their escape to deeper
water. Left on the shore, and exposed to the air, they quickly die. In confinement
they usually live but a short time, as they are very timorous and dart backward with
great velocity on the slightest ulai'm. In doing this they almost always strike the
hinder end of tlie body against the walls of the tank in which they are kept, inflicting
injuries which soon ]irove fatal. At times I have known them to leap from the tank
in which they were kept, clearing the sides, which extended eight inches above the
water.

In confinement I have watched them cajJture small fishes. They advance stealthily
towards the proposed victim by undulations of the fins, when they suddenly seize it by
means of the tentacular arms, and kill it by biting a piece out of the back of the neck
with their powerful jaws. In their natural freedom, according to Professor S. I. Smith,
they dart suddenly backward amongst the school of young fish, and then suddenly turn
obliquely to the right or left to seize their victim.

In some places they are cauglit for bait by driving the school on sho.re ; at other
times by the use of nets and pounds. This latter method is the one most adopted by
the fishermen on Cape Ann. In Newfoundland 'jigging' is the process em])loyed.
A jig is a bit of lead armed with hooks radially arranged, which is let down from the
boat and kept constantly moving up and down. This in some way exerts a fatal
fascinating power upon the squid, which seizes it, and, becoming entangled in the
hooks, they are quickly drawn to the surface. In Japan an allied species is caught in
a similar manner. The number of squid used annually in the cod fishery is almost
beyond cominitation ; a small vessel in six weeks will sometimes use eighty thousand
squid. For the ]iurposes of bait some are kept fresh, and others are salted or jtickled
in brine. As would be supposed from their being used as bait, many fish are fond of
squid, and not unfrequently schools of these molluscs which are pursuing young
mackerel arc in turn ptirsued by older fish of the same species.

In the older works many allusions are made to huge marine monsters, the descrip-
tion and figure of Pontoppidian being most frequently copied. In all of these
accounts, the animal partakes of the nature of a squid or poulpe. One of tliese early
accounts, which relates to a specimen stranded on the coast of Ireland, is more accu-
rate than most, and is withal so quaint that it deserves to be quoted here. It was
published in 1673, and is quoted from Prof. Verrill.

MOLLUSCS. 377

" The Monster Described.
" This Monster was taken at Diiigle-I-cosh in the county of Kerry, being driven
lip by a great storm in the Montli of October last 1673 ; having two heads, one great
head (out of whicli spring a little head two foot, or a yard from the great head) with
two great eyes, each as big as a pewter dish, the length of it being about nineteen
foot, bigger in the body than any horse, of the shape represented by this figure, having
upon the great head ten horns, some of six some of eight or ten one of eleven foot
long, the biggest horns as big as a man's Leg, the least as big as his wrist, which
horns it threw from it on both sides; And to it again to defend itself having two of
the ten horns plain, and smooth that were the middle and biggest horns, the other
eight had one hundred Crowns a peece, placed l)y two and two on each of them, in
all 800 crowns, each Ci'own having teeth, that tore anything that to\iched them, by
shutting together the sharp teeth, being like tlie wheels of a watch, the Crowns were
as big as a mans thumb or something bigger, that a man might put his finger in the
hollow part of them, and had in them something like a pearl or eye in the middle ;
over tliis Monster's back was a mantle of a bright Red Color, with a fringe round it,
it hung down on both sides like a Carpet on a table, falling back on each side, and
faced with white ; the crowns and mantle were glorious to behold : This monster
had not one bone about him, nor skin nor scales, or feet but had a smooth skin like a
man's belly. It swoom by the lappits of the mantle ; The little head it could dart
forth a yard from the great, and draw it in again at jilesure, being like a hawks beak
and having in the little head two tongues by which it is thought it received all its
nourishment; when it was dead and opened the liver wayed 30 pounds. The man
that took it came to Clonmel the 4tli of this instant December, with two of the horns
in a long box with the little head, and the figure of the fish drawn on a painted-cloth,
which was the full ]iroportion of it, and he went u]j to Dublin, with an intent to shew
it to the Lord Lieutenant."

"With our present knowledge it is easy to recognize this monster as one of the giant
squids, belonging, doubtless, to the genus Architeuthis . The whalers have long had
accounts of the sperm whale eating giant squid, portions of the arms being vomited
by these animals in their death flurry, but science has recognized the existence of
these huge monsters for only a few years, and for the greatest portion of our knowl-
edge we are indebted to Prof. Verrill. On our shores the first reliable account was
publislied in 1873, and merely described the jaws of a large individual found on the
Grand Banks. Since that time several specimens or parts of specimens have been
found, the number at present amounting to nearly thirty. These are at present
referred to the species Architeuthis princeps, A. harveyi., and A. inegap)tera. Some
five or six other species have been described from other parts of the world, but on our
coasts all the specimens as yet received have come from the Grand Banks, or New-
foundland. In shape, general appearance, and almost everything except size, they are
closely allied to the little species of Oinmastrep>hes, but in size the difference is enor-
mous. The Irish specimen of two hundred years ago had a length of thirty-one feet,
but apparently the tentacular arms were damaged. All of the specimens wliich have
as yet been examined by scientific men have been more or less imperfect. Yet some
of the measurements may prove interesting. One caught on the coast of Labrador,
and used as dog's meat, was said to have a total length of fifty-two feet, of which
thirty-seven belonged to the tentacular arms ; another, cast on shore at Catalina, New-

378

LOWER INVERTEBRATES.

foundland, in 1877, had a head and body nine and a lialf feet long, and tentacular
arms thirty feet in length, the circumference of the body being seven feet. This was

the specimen exhibited at the New York Aqua-
rium, and afterwards in other parts of the coun-
try. It was the best specimen ever obtained.
These large specimens all belong to the sjiecies
called A. p7-inceps. The largest specimen thus
far seen may also possibly belong to this species.
It was described by the Rev. Mr. Harvey of
Newfoundland, who has been the source of a
large amount of our information about these
monsters, and who has supjilied Prof. Verrill
with some of his specimens and much of his
data. His account, which was published in the
Boston Traveller of Jan. 30, 1879, runs as fol-
lows : —

" On the second day of November last, Stephen
Sherring, a fisherman residing in Thimble Tickle
(Notre Dame Bay), not far from the locality
where the other devil-fish was cast ashore, was
out in a boat with two other men ; not far from
the shore they observed some bulky object, and
supposing it might be jjart of a wreck, they
rowed toward it, and, to their horror, found
themselves close to a huge fish, having large
glassy eyes, which was making desperate efforts
to escape, and churning the water into foam by
the motion of its immense arms and tail. It
was aground, and the tide was ebbing. From
the funnel at the back of its head it was eject-
ing large volumes of water, this being its
method of moving backward, the force of the
stream by the reaction of the surrounding
medium, driving it in the required direction.
At times the water from the siphon was black as ink.

"Finding the monster partially disabled, the fishermen plucked up courage and
ventured near enough to throw the grapnel of their boat, tlie sharp flukes of which,
having barbed points, sunk into the soft body. To the grapnel they attached a stout
rope which they carried ashore and tied to a tree, so as to prevent the fish from going
out with the tide. It was a happy thought for the devil-fish found himself effectually
moored to the shore. His struggles were terrific as he flung his ten arms about in dying
agony. The fishermen took care to keep a i-esjiectful distance from the long tentacles
which ever and anon darted out like great tongues from the central mass. At length
it became exhausted, and as the water receded it expired.

"The fishermen, alas! knowing no better, proceeded to convert it into dog's meat.
It was a splendid specimen — the largest yet taken — the body- measuring twenty feet
from the beak to the extremity of the tail. It was thus exactly double the size of the
New York [Aquarium] specimen, and five feet longer than the one taken by Budgell.

Fig. i$2. — Archilciit/Ns jiiincvps, giant squiJ,
one fiftietli tlie natural size.

MOLLUSCS.

379

The circumference of the body was not stated, but one of the arms measured thirty-
five feet. This must have been a tentacle."

In order that the reader may obtain some idea of the size of these giants of the
Molhisca, we introduce side by side figures of the jaws of one of the common squid
(Zoligo) and of the giant squid (Architeuthis), both natural size.

Fig. 493. — Jaws of squid; A, Loligo; B, Architeuthis.

Other giant squid have been taken in various parts of the world, Iceland, Sweden,
Ireland, Japan, New Zealand, etc., but none equal in size the specimen just mentioned.
Of the h.abits of these monstei's we know nothing ; they ai-e apparently nocturnal, as
the specimens have .almost alw.ays been cast ashore in the night. It is thought that
our species frequent the deep fiords which cut the Newfoundland coasts, hiding in the
dark places during the day.

J. S. KiNGSLEY.

SPECIAL NOTICE.

The dates of issuance of the parts composing this vohime are as follows : pages
1 to 48, October 15, 1883 ; pages 49 to 144, June 12, 1884; pages 145 to 192, July 27,
1884; pages 193 to 272, December 2, 1884; pages 273 to 390, December 27, 1884;
Introduction, January 2, 1885.

INDEX.

Abalone, 320

Acauthobdella, 235

Acanthocephali, 213

Acanthometrida, 11

Acepliala, 252

Acera, 3U2

Aceste, 175

Acetabula, 360

Acalepliie, 72

Achatina, 316

AchatiniiiJE, 316

Achatinella, 316

AciculidiE, 340

Acineta, 47

Acmaja, 321

Acmajidoe, 321, 345

Acraspeda, 94

Actinaria. 48

Actinia, 113

Actiuoida, 115

Actinolophus, 32

ActinosphfEi'ium, 14

Actiuometra, 143

Actinomma, 9

Actinomonas, 22

Actinophrys, 13

Actinotrocha, 218

Actinozoa, 112

Admete, 337

Aeropese, 175

iEta, 241

^tidoj, 241

Agalma, 98

Agalmidje, 98

Agalmopsis, 102

Agauiogeiiesis, xlviii

Agassizia, 176

Agate shells, 316

Agelacriuites, 139, 140

Aglaophenia, 8G

Alasmodon, 271

Albertia, 203

Alcyonaria, 115

Alcyonidiidfe, 241

Alcyonidium, 239, 241

Alcyonoida, 121

Alectryonia, 259

Alexia, 30(i

Alternation of generations, xlviii,

97
Amaura, 346
Amblypneiistes, 170
Ambulacra, 135
Ammodiscus, 18, 21
Ammonite, 368
Ammonitidfe, 368
Amnicola, 339
Amoeba, 5

Amphiaster, xlv, 159
Amphibolidse, 305
Amphidotus, 173
Amphileptus, 28, 40
Amphitrite, 225
Amphiura, 150
Ampulla, 137
AmpuUie, 52

Ampullaria, 344
Ampullariidfe, 344
Analogy, xvi
Anancliytinse, 174
Anatinido!, 282
Anculotiis, 342
Ancylina', 307
Ancyloceras, 368
Ancylus, 308
Ancyi'omonas, 33
Anguillula, 207
Animalcules, trumpet, 42
Animal psychology, xxxi
Animals, iii
Aniso])leura, 294
Annelida, 218
Anodonta, 271
Anomia, 260
Anopla, 216
Anoplophrya, 41
Anops, 350
Antedon, 141, 142
Anthopliysa, 33
Anthroi)ology, i
Antipatliaria, 121
Antipathes, 121
Anureea, 39
Aperture, 287
Aphroditida;, 230
Apiocrinidfe, 142
Aplysia, 302
Aplysiidfe, 302
Aplysinie, 65
Apoda, 179
Apolemia, 103
A|.ok-Miiada-, 103
Aponiiais. y.M
Apsilus, 203
Apple sliells, 344
Apple snails, 344
Arachiiactis, 116
Arbacia, 167
Arbaciidae, 167
Area, 268
Arcadffi, 268
Archaic types, xviii
Archaster, 138
Arehenteron, xi
Archeteuthis, 377
Archiannelida, 219
Arenicola, 227
Argina, 268
Argonauta, 370
Aricia, 349
Ariolimax, 319
Arion, 319
Arionlna;, 318, 319
Aristotle's lantern, 165
Articulata, 247
Ascaltis, 62
Ascaridfe, 212
Asoaris, 212
Ascones, 62
Asiphonida, 257
Aspergillum, 283
Aspidocliirot£E, 182

Asplanchnidoe, 205
Asthenosoma, 168
Asthmatos, 39
Astarte, 275
Astasia, 36
AstasidiE, 36
Asteracaiithion, 160
Asterias, 160
Asteridfe, 160
Asterina, 159
Asterinidoe, 158
Asteroidea, 152
Asteropsis, 158
Astreea, 120
Astrangia, 120
Astrociiema, 152
Astroclon, 152
Astrogonium, 159
Astromma, 10
Astropecten, 158
Astropectinidae, 157
AstrophytidEB, 152
Astrophyton, 152
Astropyga, 167
Astrorhiza, 18
Astrosiga, 35
Astylospongia, 71
Atelecrinus, 144
Athorybia, 101
Athorybia larva, 101
Atlanta, 355
Atlantidse, 355
Atoll, 130
Atrocha, 203
Atrophy, xv
Auditory organ, yytt
Aurelia,' 90
Aureliidas, 90
Auricula, 30<)
Auriculidae, 305
Autolytus, 229
Avicuia, 262
Avicularia, 238
Aviculidai, 262
Azygobranchia, 322

Balanoglossus, 231
Balatro, 203

Barbed-lieaded worms, 213
Basiininuituiihora, 305
Bath-spi.iigy, 51, 64
Bathycriuus, 141)
Bear's-paw clam, 273
Beche-de-mer, 178
Bela, 337
Belemnite, 373
Belemnitidae, 373
Bellerophon, 355
Beroij, 112
BicellaridiB, 241
Bicosoeca, 34
Biniieya, 315
Bipinnaria, 155
Bittium, 348
Bivalve molluscs, 252
Black helmet, 352

381

382

INDEX.

Blastoidea, 139
Blastopore, xi
Blastostyle, 83
Blastula, ix
Bleeding tooth, 323
Blood-corpuscles, xii
Bloody clam, 268
Bodo, 33
Body whorl, 287
Boliiia, 110
Bonellia, 331
Bony tissue, xiii
Bothriocephalidse, 201
Bothriocephalus, 211
Brachiata, UO
Brachiolaria, 155
Brachionidfe, 205
Brachionus, 205
Brachiopoda, 244
Brain, xxvi, xxvlii
Brain-coral, IW
Brain-stones, 119
Brain, weight of, xxviii
Branchiobdella, 235
Breynia, 174
Brisinga, 157
BrisingidES, 157
Brissina, 175
Brissus, 176
Brit, 359
Bryozoa, 236
Buccinidse, 331
Buccinum, 332
Bugula, 241
Bulimus, 314
Bulla, 302
Bullida;, 302
Bursaria, 38, 41
Bushy sea-slug, 299
Byssoarca, 268
Byssus, 253
Bythinia, 339

Caherea, 241
Cfecum, 344
Calceolidse, 247
Calcispongiae, 61
Callista, 277
Calycozoa, 94
Calynere, 174
Calyptoblastea, 83, 87
Calyptrasa, 345
Calyptrseidse, 345
Cake urchin, 171
Camaraphysema, 61
Cameos, 351
Campaunlaridfe, 83
Canals, 287
Cancellaria, 337
Cancellaridse, 337
Capitella, 227
Caprinella, 272
Captopygus, 173
Capulus, 346
Carchesium, 45
Cardiapoda, 355
Cardiidfe, 273
Cardium, 273
Carinaria, 355
Carmaridae, 355
Carneospongiae, 63
Carrier shell, 326
Cartilaginous tissue, xiii
Carychium, 306
Caryocystites, 139
Caryop'hylteus, 198
Cas'sidae, 351
Cassidaria, 352
Cassidula, 300
Cassidulidae, 173

Cassiopea, 89, 91

Cassiopeidee, 91

Cassis, 352

Caudina, 180

Caulaster, 161

Cavolina, 357

Cellar snail, 312

Cell-division, ix

Cellepora, 243

Celleporaria, 243

Celleporidae, 242

Celleporina, 242

Cells, V

Cellularia, 241

Cellularidaj, 241

Cellularina, 241

Cephalodiscus, 244

Cephalopoda, 360

Cephalophora, 287

Cestus, 108

Ceratium, 38

Cercaria, 192, 193

Cerebratulus, 216

Cerithidea, 348

Cerithiida;, 347

Cerithiopsis, 348

Cerithium, 348

Cestoda, 198

Cestods, 198

Chsetodermse, 292

Chaetogaster, 223

Chfetognathi, 213

Chaetonotus, 206

Chaetopoda, 219

Chaetosoma, 214

Chretosomidae, 214

ChEPtospira, 42

Challengerida, 12

Chaliuula, 65

Chama, 272

Chamida^. 272

Chiaja, 111

Chilodon, 46

Chilostomata, 241

Chirodota, 180

Chirotettthis, 375

Chiton, 293

Chiton, red, 294

Chlorangium, 37

Choano-flagellata, 34

Chondrilla, 63

Chondropoma, 340

Chorion, xliv

Chromatophore, 365

Chrysogorgia, 122

Chyle, xxiii

Chyle-stomach, xx

Cidaridae, 165

Cidaris, 166

Cilia, 29

Ciliata, 39

Cilio-tlagellata, 37

Circulation, xxii

Cirratulus, 227

Cirrhoteiithis, 369

Cistenides, 225

Cladodactyla, 182

Clam, 280

, , bear's-paw, 273
,, giant, 273
,, hard-shell, 276
„ hen, 278
,, razor, 282
,, roitnd, 276
„ sea, 278
., surf, 278

Clathrulina, 13

Clausilia, 316

Clava, 79

Cleodora, 358

Clepsidrina, 23

Cliona, 66

Clione, 359

Clionida3, 359

Clitellio, 223

Clymenella, 226

Clypeastridai, 170

Clypeaster, 171

Cnidocells, 74

Cnidocil, 74

Cockles, 273

Codonella, 42

Codonosca, 33

Codosiga, 34

Coelenterata, 72

Ccelom, xii, xx

CcElopleurus, 167

Co3nurus, 201

Colacium, 37

Collosphaera, 10

Collozoa, 11

Collozomn, 9

Colobocentrotus, 169

Coloehirus, 181

Colpodella, 36

Columbellidae, 335

Columella, 287

Columbella, 335

Comatula, 142

Comatulidae, 142

Commercial sponges, 51, 64

Composite type, xviii

Comjirehensive type, xviii

Concentration of development, 59

Conchifera, 252

Concholepas, 335

Cone-in-cone, 358

Cones, 337

Conida;, 336

Connective tissue, xii

Conularia, 358

Contractile vacuole, 2

Convoluta, 190

Corals, 112

Coral, brain, 119

Coral islands, 125

Coral, organ-pipe, 123

Coral, red, 122

Coral, ruby, 122

Corallium, 122

Corbula, 87

Cordylojihora, 78

Cornuspira, 15

Correlation of organs, xiv

Corymorpha, 81

Cotiiurnia, 27, 45

Conus, 336

Cowries, 348

Crambactis, 115

Cranchia, 375

Cranchiidae. 375

Craspedota, 94

Crania, 246

Craniida;, 246

Crenella, 267

Crepidula, 345

Creseis, 358

Cribrella, 160

Crinoidea, 139

Crisia, 240

Crisiadae. 240

Cristatella, 243

Cristatellidas, 244

Crossaster, 160

Crucibulum, 345

Crumb-of-bread sponge, 66

CryptDilon, 274

Crystalline cones, xxx

Crystalline rods, xxx

Crystalline style, 254

INDEX.

383

Crystallodes, 1C2
Ctenobranchia, 324
Ctenodiscus, 158
Ctenophora, 108
Ctenostomata, -41
Cucumaria, 181
Culcita, 159
Cuuina, 88

Cup-and-saucer limpets, 315
Cup sponge, 04
Ciittle-lione, 374
Cuttle-fish, a74
Cuvieria, y08
Cuvierian organs, 177
Cyanea, 90
CyanidfB, 90
Cyathomonas, 33
Cycladidai, 275
Cyclas, 274
Cyclocardia, 376
Cyclophorus, 340
Cyclostoma, 340
Cyclostomata, 240
CyclostomidEe, 339
Cyclotus, 310
Cydippe, 111
Cylichna, 302
Cyllndrellidte, 310
Cymbium, 327
Cymbulia, 359
Cymbulida;, 358
Cyprseidfe, 348
Cyrenia, 275
Cyrenidoe, 275
Cyprina, 275
Cyprinldse, 275
Cystechinus, 174
Cysticercus, 199
Cystidea, 139
Cystobranchus, 235
Cytherea, 277
Cytode, vil

Dactylocalyx, 71
Dactylometra, 92
Dactylozooid, 88
Darts, 305
Darwinella, 04
Darwinian theory, liii
Darwinism, liii
Dead-man's-fingers sponge, 65
Decacera, 372
Decapoda, 372
Degeneration, xv
Delainination, xi
Del|>himila, 323
Dcnitrochiiota!, 181
Dendrocoela, 188
Dendronotns, 299
Dentaliida;, 291
Dcntalium, 291
Desmarella, 35
Desmoscolocidie, 215
Desmoscolex, 215
Desmosticha, 164
Desmoteuthidfe, 375
Desmoteuthis, 375
Deutoplasm, x
Devil-fish, 371
Dextral, 304
Diadema, 107
Diadematidre, 167
Diasterina, 159
Diastoporidre, 240
Dibranchiata, 369
Diceras, 272
Dictyophora, 203
Dicyema, 196
Dicyemennea, 196
Dicyemidae, 196

Dicystidea, 25

Differences between plants

animals, ill
Difflugia, 6
Digestion, xix
Diglena., 205
Dimastiga, 32
Dimorphism, xlix
Dimyaria, 257
Dinobryon, 37 ,

Diopatra, 225
Diphyse, 105
Diphyes, 105
Diphyidoe, 105
Diploblastic, xi
Diploria, 119
Diplostomidea, 183
Diplozoon, 194
L)iporpa, 195
Discida, 10
Discina, 246
DiscinidiB, 246
Discoidese. 107
Discophora, 89
Discophori, 232
Discoporidaj, 242
DistomeiE, 194
Distomnm, 191
Dochmins, 211
Doliid^, 352
Dolium, 'Xhi
Donax, 280
Doridida;, 301
DoridopsidiB, 301
Doris, 301
Dorocidaris, 166
Dorylaimus, 209
Dosinia, 277
Doto, 299
Dracunculus, 209
Drainage system, 53
Drcisseua, 267
Drill, 331
Dnthiersia, 201
Dycistidea, 24
Dysidea, 05
Dysteria, 46

Ear-shells, 320
Ear-vesicles, xxx
Earth-worm, 220
Eburna, 333
Ecardinia, 240
Echinanthus, 171
Echinarchuius, 171
Echinaster, 159
Ecliinasteridte, 159
Echinida3, 109
Echinocardium, 174
Echinocrepis, 174
Echinocyamus, 171
Echinoderes, 206
Echinoidea, 161
Erliinometra, 169
Echinonemata, 66
EchinometridfE, 169
Eebinorhynchns, 213
Ecliinothrix, 107
EcliinothuridBe, 168
Echinus, 170
Echiuridae, 231
Echiuris, 231
Ectoderm, x
Eotoprocta, 240
Ectosarc, 5
Echinodermata, 136
Edrioaster, 139
Edwardsia, 116
Egg, ix, xliv
Elasipoda, 179

Elasmopoda, 179
and I Elastic tissue, xiii A
Eledone, 372
Eleutheroblastea, 77
Elpidia, 179
Elysia, 298
Elysiella, 298
Elysiidoe, 298
Embryology, xllr
EnchytrBeidse, 225
Encope, 172
Encystment, 3
Endoblast, x
Endocepliala, 252
Endoderm, x
Endoplast, 27
Endosarc, 5
Enopla, 216
Enoplida;, 209
Enoploteuthis, 375
Enoplus, 209
Ensis, 282
Entails, 291
Enteron, xx
Enteropneusti, 231
Entoconcha, 295, 343, 347
Entoprocta, 239
Entosphserida, 11
Eolidse, 298
Eolis, 299
Eozoon, 4, 21
Ephyra, 96
Epiblast, X
Epiderm, x
Epiphragm, 304
Epipodia, 249
Epipyxis, 37
Epistylis, 33, 45
Epithelial tissues, xii
Errantia, 228
Escharina, 242
Eschariporidae, 242
Eulima, 343
Euplectella, 08
Euryale, 152
Eustomata, 36
Encecryphialus, 9
Euchone, 226
Euclypeastridse, 171
Eucrate, 241
Eucratida;, 241
Eucyrtidium, 11
Endendrium, 79
Euglenidse, 36
Euglena, 31,36
Eupleura, 331
Euplotes, 27, 47
Eupyrgus, 179
Eustrongylus, 211
Enthyneiira, 294
Evolution, lii
Exogyra, 260
Eyes, XXX
Eye-spots, xxx
Eye-stones, 288

Farella, 241
Fasoiolaria, 331
Female pronucleus, xlv
Fertilization, xlvi
Fibrous-tissue, xiii
Ficula, 352
Fig-shells, 352
Fiiaria, 209
Filaridse, 209
Firola, 3.56
Firoloides, 356
Fissurella, 320
Fissurellids!, 320
Flagellata, 31

384

INDEX.

Flagellifera, 11
Floscularia, 201
Floscularians, 20i
riustra, 242
riustrina,, 242
Fluviatilidii!, 67
Folliculina, 42
Food vacuole, 2
Foot, 287
Foramnifera, 15
Forskaliada;, 102
Fulgor, 3ol
Fuugia, 117
Fusiiiae, 331
Fredricella, 244
Fresh-water limpets, 308
Fresh-water mussels, 269
Fresh-water sponges, 67

Gadinidic, 305
Ganglion, xiii
Garden-snail, 313
"Gapes," 211
Gasteropoda, 292
Gasti'ocheenidiE, 283
Gastrojihysema, 01
Gastrotricha, 206
Gastrula, x
Gattulina, 21
Gelatinous tissue, xii
Gemellaria, 241
Generalized tj^pes, xvii
Gemma, 277
Geodia, 68
Geomaiism, 50
Gephyi-ea, 217
Gephyrei Chfetiferi, 217
Giant clam, 273
Giant squid, 377
"Gid," 201
Gills, xxiv
Glandina, 310
Glands, xxi
Glass-rope sponge, 69
Gleba, 106
Glenodinium, 38
Globigerina, 19
Globigerina ooze. 19
Glochidium, 270
Glycimeris, 281
Giiathobdellidae, 233
Gnathodon. 279
Gold-shell, 200
Gonangia, 78
Goniasterida^, 159
Goniobasis, 342
Goniocidaris, 166
Gonotheca, 83
Gonothyrea, 84
Gordiida;, 212
Gordius, 212
Gorgonocepbalus, 152
Gorgonidfe, 122
Graptolites, 80
Gregarina, 25
Gregarinida, 23
Gromia, 14, 15
Growth, viii
Gryphasa, 260
Guard, 373
Guinea-worm, 209
Gumminia. 63
Gummininfe, 63
Gundlachia, 308
Gymnoblastea,.77
Gymnocyta, 2(i
Gymnodinium, 38
Gymnolfpniata, 240
Gymnosomata, 359

Hsemodipsa, 234
Haemopsis, 234
Hair-worm, 212
Halcyonium, 122
Halcyouoida, 115, 121
Halcyonid*, 122
Halichondria, 06
Haliomma, 10
Haliotida;, 320
Haliotis, 320
Halisarca, 63
Halisarcoidea, 63
Halisphysema, 61
Halistemma, 102
Halophragmium, 18
Halteria, 43
Haminea, 302
Hammer-shell, 265
Hard-head sponge, 64
Hard-shell clam, 276
Harpa, 329
Harp shells, 32'J
Hastigerina, 20
Hauptzoiiid, 124
Hay-fever, 39
Hearing, xxx
Heart, xxiii
Hectocotylus, 365
Heliaster, 160
Heliastraja, 119
HelicidsE, 310
Helicina, 324
Helicinae, 313
Helicinida;, 324
Heliozoa, 4, 13
Helix, 313
Helmet-shells, 351
Hemiaster, 175
Hemicardium, 274
Hemicystites, 139
Hemiophrya, 30, 48
Hemphillia, 310
Hen-clam, 278
Herma;a, 299
Hermione, 230
Herpetomonas, 33
Heterocentrotus, 169
Heteronereis, 228
Heteroteuthis, 375
Heteropoda, 353
Heterotricha, 41
Hexactinellinfe, 69
Hexametra, ?A
Hipponoe, 170
Hipponyx, 34{>
HippopodifB, 105, 106
Hippopodius, 106
Hippopus, 273
Hippurites, 272
Hippuritida% 272
Hirudinei, 232
Hirudo, 233
Histioteuthis, 375
History of Zoology, Ixiv
Histriobdella, 235
Holopus, 140
Holostomata, 338
Holothuria, 182
Holothuroidea, 176
Holotriclia, :'.!•
Holtenia, 70
Homolampas. 174
Homology', xvi
Horse-sponge, 64
Hyaleidse, 357
Hyalina. 357
Hyalouema, 09
HVbrids, 1
Hydatina, 205
Hydra, 73, 77

Hydractinia, 82, 89
Hydranth, 78
Hydrocorallinre, 88
Hydroid, 73
Hydroidea, 73
Hydrorhiza, 78
Hydrollieca, 83
Hydrozoa, 73
Hymenaster, 157
Hyocrinus, 146
Hypoblast, x
Hyponome, 140
Hypotrieha, 46

lanthinid^, 325
lothydium, 206
Icthyobdella, 235
Idmonea, 241
Idol-shells, 345
Ilyanassa, 333
Impregnation, xlvi
Inarticulata, 24(i
Individual, 57
Inermes, 217
Infundibulum, 346
Infusoria, 26
Ink-bag, 363
Inorganic bodies, ii
Intseniolata, 87
Integropalliata, 257
Intestine, xx
In^■agiuation, x
lo, 342
Irpa, 179
Isidse, 123
Isis, 123
Isocardia, 376
Isogeny, xvil
Isopleura, 292
Ivory shells, 333

Jelly-fishes, 89
Jointed worms, 218

Kellia, 279

Key-hole limpets, 320
Kerato-silicoidea, 65
Ivcratode. 63
KcnilMidea, 64
KiriUkeiimoddings, 257
Kolga, 179
Koonsia, 303
Korethraster, 157
Kraken, 369

Labial palpi, 254
Lachrymaria, 40
Lacuna, 339
Lacustridfe, 67
LEevicardium, 273
LagansBca, 35
Laganum, 171
Lagena, 15
Lagenophrys, 45
Lamarckianlsm, Ivi
Lamcllaria, 347
LamellibriVnchiata, 252
Lana di mare, 103
Land leeches, 234
Land snails, 311
Laival forms, xlvii
Lasso cells, 74
Leda, 269
Leeches, 232

land, 234
Lepardia, 242
Lepeta, 321
Lepidonotus, 230
Lepocyta. 26
Leptodera, 207

INDEX.

386

Leptodisous, 37
Leptomonas, 33
Leptychaster, 158
Leskiiuie, 173
Leucones, IJ3
Ligula, 108
Lima, 2()1
Limacidae, 317
Liinaciiia, 359
Limaciiije, 31!)
Liinacinidfe, 358
Liinax, 305, 319
Limiuote, '3'23
LhnnsBa, 307
Limnjeidae, 307
LimiiEEinas, 307
Limpets, 321, 345

,, cup and saucer, 345

fresli water, 308
„ key-hole, 320
,, slipper, 345
Linckia, 1511
Ijiiickiadse, 159
Liuerses, 93
Lingual ribbon, 288
Lingula, 24()
Lingulella, 24(5
LingulidsE, 24U
Llpocephala, 252
Lip, 287
Lithistlnse, 69
Litbodomus, 267
Litlorina. 338
Llttorinldfe, 338
Liver Huke, 191
Lizzla, S'i
Lobosa, 5
Locomotion, xix
Lollginldie, 374
Loligo, 374
Loligopsidfe, 375
Loligopsis, 375
Loliolus, 374
Lopbomonas, 34
Lophopbore, 237
Lopbopus, 244
Lottia, 321
Lovenia, 174
Loven's larva, 219
Loxosoma, 240
Lucernarla, 94
LucernaridK, 94
Lucina, 274
Lucinidse, 274
Lug-worm, 227
Luidia, 158
Lumbriculus, 224
Lumbricus. 220
Lunatla, 34G
Lungs, xxiv
Luponla, 349
Lympbatics, xxili
Lyonsia, 282

Macoma, 280
Maorocyclis, 312
Macrostomum, 234
Mactridse, 278
Madrepora, 117
Madreporic body, 135
Magihis. ;>;;5
Maiac.jlj.lrlla, 235
MaldanbUt, 226
Malleus, 265
Malpigian vessels, xx
Mamma, 346
Manaytinkia, 227
Manicina, 120
Mangelia, 337
Mantle, 249

Maretia, 174
Margarita, 322
Margaritana, 271
Marginella, 327
Martesia, 286
Maryiia, 40
Mason sbell, 326
Mastigocerca, 205
T\Iasti-aiu.i.-ba, 27, 32
M;\sti,uotcutbis, 375
Jlaturation of egg, xlv
Meandrina, 119
Meconidium, 85
Mediaster, 159
Medusa, 78
Melanipus, 306
Melania, 341
Melaniidfe, 341
Melaniinae, 341
Melantbo, 340
Meleagrina, 262
Melicerta, 204
Mellita, 172
Melitasa, 123
Melo, 327

Membranipora, 242
Mental cliaracteristics, xxxi
Mirmis, 2li
Mennitliidje, 212
Meroc, 277
Mesenteron, xi
Mesoblast, xi
Mesoderm, xi
Mesopodium, 249
Mesostomum, 190
Metamorpbosis, xlvi
Metapodium, 249
Metazoa, 49
Metridium, 113, 116
Mierostumidas, 191

Mi,.'r,,i;i<)iia, 66

MycropUylc, xlv

Millepora, 89

Millepore corals, 88

Miliola, 21

Mind, xxxi

Mitra, 329

Mitridfe, 329

Mnemiopsis, 110

Modiolus, 266

MoUusca, 248

bivalve, 252

naked, 295

,, wing tooted, 356

Molluscoidea, 236

Molpadia, ISO

Mouactinellinfe, 66

Monadidie, 32

Monas, 33

Moner, 3

Monera, 2

Mouocaulis, 81

Monocerca. 205

Moaocystidea, 24, 25

Monodonta, 323

Monomastiga, 32

Monomyaria, 257

Monosiga, 35

Monoxenia, 113

Montacuta, 279

M.mtagua, 299

M.i|,sr;i, 123

Mimiteutbis, 375

Morpbology, ii

Morula, ix

Month, 287

Mulinia, 279

Mulleria, 182

Murex, 330

MuricidsE, 330

Muricinse, 330
Muscular tissue, xiii
Mussa, 120
Mussels, 264

,, fresh water, 269
Mutton fish, 93
Mya, 280
Mycedium, 117
Myidfe, 2S0
Myriotrochus, 179
Myriozoidae, 242
Myriozoum, 242
Mytilida?, 266
Myxobrancbea, 9
Myxospongia;, 63
Myzostoma, 231

Naiadaa, 269

Naidae, 223

Nais, 223

Naked molluscs, 295

Nassa, 333

Natica, 346

Natural History, i

Natural selection, liii

NautilidiE, 368

Nautilus, 104, 368

Navicella, 323

Nectooalyx, 99

Nectostem, 99

Nematoda, 207

Nematogens, 197

Nemertea, 215

Nemertes, 216

Neo-Lamarckianism, Ivi

Neomenia. 292

Neomenoidea, 292

Nephelis, 234

Nephridia, 251

Neptbyda;, 228

Neptunea, 331

Nereida3, 228

Nereis, 228

Nerinsea, 342

Nerita, 323

Neritidai, 323

Neritina, 323

Nervous tissue, xiii

Nerves, xxiv

Neverita, 346

New England sea-urchin, 169

Nidorellia, 159

Noah's ark, 268

Noctiluca, 25, 30, 37

NoctilucitlEe, 37

Nonionina, 16, 20

Noteus, 205

Notommata, 205

NuculidfE, 269

Nuda. Ill

Nudibranchiata, 295

Nuclear vesoicle, 8

Nucleolus, viii, xlv

Nucleus, viii, xlv

Nucula, 269

Nummulina, 17

Obelia, 83
Obolus, 246
Octopoda, 369
Ootopodidae, 370
Octopus, 370
Ocyroe, 109
Odontopliore, 288
Odostomia, 342
Oisopbageal ring, xxvi
Oesophagus, XX
Oleacinidae, 310
Oligocbffita, 220
Oligotrochus, 180

386

INDEX.

Oliva, 32S
Olive shells, 328
Olivella, 329
OlividiE, 328
Olyntlioidea, 62
Omniasli'epliuliE, 375
Oininiislreplies, 37(i
Oncliitlella, .M)
Onchidiida!, 309
Onchidium, 309
Onchidoris, 301
Oniscia, 352
Onycliotentlils, 375
Opalina, 41
Opercularia, 45
Operculum, 288
Opliiacantha, 151
Opliiactis, 15(1
Opliidaster, 159
Opbidomonas, 33
Ophiobyi'sa, 152
Ophioceramis, 149
Ophiociasma, 152
Opliiocoma, 151
Opbiocnida, 150
Ophiocreas, 152
Opliiocteu, 149
Opliiocyinbium, 151
Opiiioglypba, 149
Opiiioliclus, 152
Opbiomitva, 151
Opbiomusium, 149
Opliiomyces, 152
Opbiomyxa, 152
Opbionella, 45

Opbiopbolis, 150

Opbiotbrix, 151

Ophiozona, 149

Opbiui-a, 149

Opbiuvid(is>, 148

Opbiuroidea, 147

Oplu'ydiiiEe, 4-3

Opbrydium, 27, 45

Opbryocotyle, 201

Opbyomyces, 152

Opisthobraiicbiata, 295

Orbiouliiia, Ki

Orbitnlites, 16

Orbulina, 20

Oreaster, 159

Organic bodies, ii

Organ-pipe coral, 123

Organs, xiii

Organs, correlation of, xir

Organs of Bojanus, 251

Orniers, 320

Ortbidaj, 247

Orthoceras, 3G8

Ostrea, 257

Ostreidaj, 257

Ostrich plume, 86

Otina, 307

Otocysts, XXX, 84

Otoliths, XXX

Ovulum, 349

Oxygyrus, 355

Oxyu'ris, 212

Oyster, 257

pearl, 262 .
thorny, 262

Pachybatron, 352
Pachydrilus, 223
Pacbytrocha, 45
Pallets, 283
Pallial chamber, 288
Pallial Hne, 256
Pallial sinus, 257
Pallium, 249
Paludicellida;, 241

Paludina, 340
Paludinida;, 340
Palythoa, 69
Pandora, 282
Panopsea, 281
Pantostomata, 32
Paper nautilus, 370
Paper sailor, 370
Papliia, 280
Parallelipedum, 268
Paramecidse, 39
Paramecium, 28, 39
Parapodia, 219
Parasira, 370
Partula, 315
Parthenogenesis, xlviii
Parypba,"S0
Patella, 320
Patellida?, 320
Patiria, 159
Peacbia, 116
Peacock tail volute, 327
Pear-shells, 352
Pear-snail, 332
Pearl oyster, 262
Pearly nautilus, 308 '
Pecten, 261
Pectinaria, 228
Pectinatella, 244
Pcctinida;, 260

Pectinura, 149

Pectunculus, 269

Pedata, 180

Pediceilaria, 153

Pedicellina, 239

Pedicellinidfe, 239

Pedipes, 306

Pelagia, 92

Pelagidaj, 92

Pelecynoda, 252

Pelican's-foot shell, 351

Pelodera, 207

Peneropolis, 16

Pennaria, 80

Pennatula, 123

Pennatulida;, 123

Pentaceros, 159

Pentacrinns, 142

Pentacta, 181

Pentremites, 139

PerichEeta, 222

PeridinidiE, 38

Peridinium, 38

Perinopsis, 172, 176

Periphylla, 5)4

Peripbyllidfe, 94

Periploma, 282

Perisarc,77

Peritricba, 43

Perivisceral space, xx

Periwinkles, 338

Perna, 266

Peronia, 309

Person, 57

Perspective shell, 326

Petalosticha, 172

Petricola, 277

Petricolida", 277

Petrified fingers, 373

Phalansterium , 35

Pharetrones, 63

Pbascolosoma, 217

Pbasianella, 323

Pheasant shells, 323

Pheronema, 71

Philinida;, 302

Philonexidfe, 369
Phileus, 162

Pholadidea, 286
Pholadina), 283

Pholas, 285
Phormosoma, 168
Phoronis, 218
Phorus, 326
Phosphorax, 319
Phragmocone, 373
Plireoryctes, 223
Pbreoryctidae, 222
Pliylac'tolaimata, 243
Pbyllacanthus, 166
Pbyllididfe, 298
Phyllirhoe, 300
Phyllirhoida?, 300
Phyllodoce, 229
Physa, 308
Physalia, 104
Physemaria, 61
Physiology, xviii
Physophora, 102
PhysophoriB, 98
Physophoridfe, 102
Pilgrim's shells, 261
Pilidium, 217
Pin-worm, 212
Piima, 87, 267
Pisidium, 275
Placuna, 2()0
Planaria, IfcS
Planorbinje, 307
Planorbis, 308
Plant, iii

Plants and animals, differences
between, iii

Planula, 78

Plastidules, 4

Plathelminthia, 187

Platycola, 33, 45

Platycrinus, 146

Platytheca, 33

Pleurobracliia, 111

PleurobranchidEe, 303

Pleurobrancbea, 295, 303

Pleuro-peritoneal cavity, xii

Pleurotoma, 337

PleurotomtridiE, 323

Pleurotomid.ne, 337

Plumatella, 244

Plumularia, 86

Plumularida;, 86

Pneumatophoia;, 104

Pneumodermon, 3G0

Pneumodermonida;, 360

Pneumophora, 180

Podocyrtis, 12

Podop'hrya, 47

Podophryse, 47 '

Podostoma, 32

Podostomata, 244

Polar globule xlv

Folia, 216

Polian vescicle, 137

Polycelis, 189

Polycera, 300

Polyoerida;, 300

Polycb^ta, 225

Polycirrus, 235

Polyclonia, VI2

Polycystina, 8, 11

Polyd'ora, 227

Polygastrica, 6

Polygordius, 219

Polykrikos, 40

Polymastiga, 32

Polymorphism, 49

Pol'ya'Ca, 35

Polyps, 112

Polyp stem, 99

Polvpides, 237

Pol'ypites, 100

Polyplacophora, 293

INDEX.

387

Polystomerp, 194
PolystoiUfUa, lU
Polystomum, 195
Polyzoa, 1330
Pomatiopsis, 339
Pompholyx, 308
Pond snails, 307, 340
Pontobdella, 235
Pontolimax, 298
Porcelain shells, 348
Porcellanaster, 153
Poviferata, 49
Porocidaris, 163
Porospora, 24
Poriiita, 107

Poi'tiiguese niau-of-war, 104
Potamides, 348
Potamospongiae, 67
Poulpe, 371
Pourtalesia, 173
Praya, 10)
Prayida;, 106
Precious wentle trap, 323
Priapulidre, 218
Priaimlus, 218
Primitive stomach, xi
Prionechiims, 170
Proboscidii'era, 324
Productidjc, 247
Proslottids, 198
Proneomeiiia, 233
Pronucleus, xlv
Prophetic type, xviii
Prophysaon, 319
Propodium, 249
Prosperpina, 324
Protamteba, 25
Proteids, vi
Protista. 2
Protohydra, 77
Protomyxa, 3
Protoplasm, v
Protoplasta, 4, 14
Protospongia, 35, 71
Protozoa, 1
Psammobia, 280
Pseudodifflugia, 15
Pseudopodia, 5
Pseudospora, 34
Psolus, 181
Psorosperma, 25
Psychyology, xxxi
Ptenoglossa, 324
Pteraster, 139, 157
Pterasteridae, 157
Pterocera, 350
Pteropoda, 336
Pterotrachea, 356
PterotracheidfB, 355
Pullenia, 20
Pulmonata, 30'!
Pulmonifera, 303
Pupa, 316
PupidiE, 316
Purple shell, 325
Purpura, 3;J4
Pycuopodia, 160
Pyi-amidella, 342
Pyramidellidre, 342
Pyrazus, 348
Pyrula, 331
Pyxicola, 45

Quahog, 276
Quill, 261

Radial canal, 137
Radiata, 135
Radio-tlagellata, 32
Radiolaria, 7

Radiolarian ooze, 21
Kanrlhi. '-'Cio
Kan.^i:l, 279
Rapaiia, 335
Rataria, 107, 108
Razor clams, 282
Recluzia, 325
Red chiton, 294
Red coral, 122
Redia, 192
Renilla, 124
Reproduction, xliv
Respiration, xxiii
Respiratory tree, xx, 177
Retepora, 243
Reteporidas, 243
Reticularia, 14
Rhabditis, 208
Rhabdocoela, 190
Rbabdogaster, 214
Rhabdoplev.ra, 244
Rhabdostyla, 45
Rliachi-lussa, 327
Rhapliidonemata, 65
Rhipidogorgia, 122
Rhizochilus, 335
Rhizocrinus, 142, 146
Riiizo-tlagellata, 31
Rhizophysa, 104
Rhizopoda, 4
Rhombogens, 197
i;iio|pali>dina, 183
i:iiviiclH-t;i, 47
Rhynrlioljilellidfe, 234
Rhynchonella, 247
Rhynclionellidfe, 247
Rhyncopygus, 173
Ring canal, 137
Rissoa, 339
Rissoella, 339
Rissoid.'e, 339
Roman snail, 313
Rossia, 375
Rostellaria, 350
Rostrum, 373
Rotalia, 16, 21
Rotella, 323
Rotifer, 202
Rotifera, 202
Round clam, 276
Round worms, 212
Rudistes, 272

Sagitta, 214
Salenia, 167
Salenida3, 167
Salpingceca, 35
Sand dollar, 171
Sand saucers, 346
Saugiiinolaria, 280
Sarcodictyon, 124
Saxicava, 281
.Scalari(l:e. 326
Si';Ul..ps, 260
Scapluu-ca, 268
Scaphopoda, 291
Scarabus, 306
Schizaster, 176
Schizosiphon, 46
Schizostoma, 342
Scorpion shells, 350
Scrobicularia, 280
Scurria, 321
ScutellidjE, 171
Scutibranchia, 322
Scvandra, Ii2
Si'Vn.'a, 299
Scyphistoma, 96
Scyphostoma, %
Scytomonas, 33

Sea-anemone, 113, 115
Sea-blubs, 89
Sea-corn, 333
Sea-clani, 278
Sea-fans, llii, 121
Sea-hare, 303
Sea-cucumbers, 176
Sea-nettles, 89
Sea-pens, IKi
Sea-urchins, IGl

New England, 169
Sea-wash-balls, 333
Sea-wliips, 121
Segmental organs, xx
Segmentation, ix

,, cavity, ix

,, nucleus xlvi

Seison, 203
Semele, 280
Sensations, xxiv
Sense of touch, xxx
Sense organs, xxx
Sepia, 374
Sepiadoe, 374
Sepiola, 375
Sepiolida;, 374
Sepioteuthis, 374
Septaria, 285
Serpent stars, 147
Serpula, 226
Serpulidfe, 226
Serripes, 274
Sertularia, 86
Sertularidos, 86
Setfe, 29
Shell, 249

,, agate, 316

,, apple, 344

,, carrier, 326
• „ ear, 321

„ fig, 352

„ gold, 260

,, hammer, 265

„ harp, 329

,, helmet, 351

,, idol, 345

„ ivory, 333

,, mason, 326

„ olive, 328

,, pear, 352

,, pelican's foot, 351

„ perspective, 326

,, pheasant, 323

,, pilgrim's, 261

,, porcelain, 348

,, purple, 325

„ scorpion, 350

,, silver, 260

,, sun dial, 320

„ tooth, 291

,, top, 322

,, tun, 352

,, weaver's shuttle, 349

,, wing, 349
Ship-worm', 284
Sigaretns, 347
Sight, xxx
Silicoidea, 68
Siliqua, 283
Silver shell, 260
Sinistral, 304
Sinnespolster, 91
Sinupallialia, 257
Sipho, 331
Siphon, 253, 360
Siphonarida?, 305
Siphonida, 257
Siphonophora, 97
Siplionopoda, 291
SipunculidiB, 217

388

INDEX.

Slipper limpet, 345
Slugs, 317
Snails, oil
Snail, ap[)le, 344
,, cellar, ;il2
,, garden, '.iVi
„ land, 311
,, pear, 332
,, Koman, 313
„ poud, 240, 307
Solaridae, 3'25
Rulaster, 159
Solciii,vi;i, 283
Solon, ■1>^'1
Solenidai, 282
Solenopliorus, 202
Spadella, 214
SpatangidiB, 173
Spatangina!, 174
Spatangocystis, 174
Spatangus, 174
Specialized types, xvii
Spectre candles, 373
Spicules, sponge, 54
Sperniatophores, A&a
Spermatozoan, ix
SphiEridia, lfi2
Spha^rium, 275
Splia'rodina, 20
Sphn-rophrya, 47
Siili;rro/,(Hun, 12
Spii'iila anioris, 305
Spicules, 54
Spindle, xlv
SpiriferidiE, 247
Spinalis, ;158
Spirillina, 18
Spiroclionia, 45
Spirorbis, 227
Spirostomum, 27, 41
Spirula, 373
Spirulida;, 373
Spondylus, 202
Sponges, 44
Sponge, bath, 51, 04

,, commercial, 64

,, crumb-o£-bread, 60

,, cup, fi4

,, dead-man's finger, 65

,, hard-head, G4

,, fresh-water, 67

„ glass, liil

„ horse, 04

,, spicules, 54

,, toilet, 04

,, wool, G4

Zimmocca, 64
Spongina;, 64
Spongomonas, 36
Squid, 300, 374, 376
Squid, giant, 377
" Staggers," 201
Star-fishes, 152
Statoblasts, (i7, 238
Stauroteuthis, 3(i9
St. Cuthbert's beads, 139
Stellerida, 147
Stentor, 28
Stephanomia, 102
Stephanops, 205
Stern apsis, 227
Stichopns, 182
Stichotricha, 46
Stinging cells, 74
Stoastoina, 324
Stomatoca, 83
Strepomatinne, 342
Streptaxis, 310
Streptoneura, 294 319
Strigilla, 279

Strobila, !X5
Strombidre, 349
Strombs, 350
Strombus, 350
StrongylidsE, 211
Strongyloceutrotus, 170
Stylets, 29
Styliter, Ul
Styliola, 3D8
Stylommatophora, 309
Stylonichia, 45
Suberites, 6()
Succinea, 317
Succinidie, 317
Suckauliock, 277
Suctoria, 47
Sun-animalcules, 13
Sun-dial shell, 32l)
Sun-fish, 89
Sun-star, lUO
Supply system, 53
Surf-clam, 278
Sutures, 287
Sycandra, 55
Sycones, (i2
Sycotypus, 131
Syllidaj, 229
Synapta, ISO
Synaptida;, 180
Synaptula, 180
Syngamus, 211
Synthetic type, xviii

Syzygy. i-i-t

Tactile sense, xxx
Taenia, 198
Tasnioglossa, 338
Taonius, 375
Tapes, 277
Tape-worms, 198
Tebenoplioriufe, 318
Tebenophorus, 318
Tectibranchiata, 301
Teeth, xxi
Telescopium, 348
Tellina, 279
Tellinidie, 279
Tentaculata, 111
Tentaculifera, 47
Terebella, 225
Terebellum, 350
Terebra, 337
Terebratulid.'e, 247
Terebratulina, 247
Teredinaj, 284
Teredo, 284
Tergipes, 298
TererbridiE, 337
Testacella, 310
Testacellidaj, 310
Testicardina, 247
Tethya, 68
Tethys, 300
Tetrabranchiata, 307
Tetractinellina?, 08
Tetrastemma, 215
Teuthidse, 375
Textularia, 16, 21
Thalassema, 231
Thalassicolla, 7
Thalassolampe, 9
Thamnocnidia, 81
Thecata, 87
Tbff'idium, 247
Th(ros(.iii:ita, 357
Thimble-lisli, 93
Thorny-oyster, 262
Thracia, 282
Thunder-bolts, 373
Thuricola, 45

Thvone, 181
Thyoiiidium, 181
Thysanozoon, 189
Thysanoteuthis, 375
Tiedemannia, 359
Tintinus, 42
Tissues, ix, xiii
Tube-worm, 225
Toilette sponge, 64
Tomopteris, 230
Tongue, 288
Tooth shells, 291
Top-shells, 322
Tornatella, 302
Tornatellidie, 301
Torquatella, 43
Toxiglossa, 330
Trachelocera, 36, 40
Tracheloceridae, 40
Trachelomonas, 37
Trachydermon, 294
Trachymedusas, 88
Trachvnema, 88
Trematoda, 191
Tricliaster, 152
Trichina, 210
Trichinosis, 210
Tricbocephalus, 365
Trichocysts, 27, 40
Trichodina, 43
Trichonella, 03
Trichouymijliids, 41
TricliotrachelidiE, 210
Trichocephalus, 211
Tridacna, 272
Ti-idacnida;, 272
Triforis, 348
Trigonia, 209
Trigonidse, 269
Triploblastic, xi
Tritia, 333
Tritonidse, 352
Tritonium, 353
Trivia, 349
Trochosphcre, 251
Trochostoma, 179
Trochozoon, 186
Trochammina, 21
Trochida;, 322
Trochus, 322

Trumpet animalcules, 42
Truncatella, 340
Trochoceras, 308
Trychonymijha, 41
Trypanosoma, 31
TrVpanosomata, 31
Tuba, 60
Tubioolfe, 225
Tubifex, 223
Tubificidfe, 223
Tubipora, 121, 123
Tubiporida', 123
Tubularia, 81
Tubulipora, 240
Tubuliporida;, 240
Tulotoma, 340 '

Tun shells, 352
Turbellaria, 188
Turbo, 322
Turritellida?, 343
Turritopsis, 88
Tvlenchus, 208
Tyrian purple, 330, 334
Types, xvii

Umbellularia, 124
UmbellulidiE, 124
Umbilicus, 287
Umbrella, 303
Uncini, 29

INDEX.

389

Ungulina, 279
Unio, 270
UnionidiB, 269
Ureciiiiius, 174
Uniatella, 239
Unmla, il
Ui'osalpinx, 331
lUi-icularia, WO
Uvella, :S7

Vagiiiicola, 45
VaginicoliiiJB, 43, 45
Valvata, :J45
Valvatiilae, 345
Varices, 330
Velella, 107
Veliger, 152
Yeliiiu, 251
VeneriiUt, 37(j
Ventriculites, 71
Venus, 27G
Venus' Hower-basket, C8

., girdle, 108
Vermes, 185
VermeticltG, 343
Vermetus, 344
Veronicella, 310
Vertigo, 316
Vescicularia, 241
Vescicularidae, 241
Vesciculata, 12
Vibracula, 238
Vinegar eels, 207

Vitelline membrane, xliv
Vitrina, 312
Vitrininae, 312
Voluta, 327

Volute, jjeacock-tail. 327
Volutes, 327
Volutida;. 327
Volutomitra, 330
Vortex, 190
Vorticella, 43
Vorticellidfe, 43
Vorticellinaj, 43

Waldhamia, 245, 247
Wanipum, 277
Watering-pot, 283
Water-vascular system, xxiii
Water-%'ascular canal, xx
Weaver's shuttle shell, 349
Wentle-trap, 321)

,, precious, 326

Whale's tongue, 231
Wlieat-worm, 208
Wheel-animalcules, 202
Whelk, 333
Whorls, 287

Wing-footed mollusca, 35G
Wing-shells, 349
Wool sponge. 64
Worms. 185

Worm, barbed-headed, 213
earth, 220

Worm, hair, 212
„ .iointed, 218
.. lug, 227
.. pin, 212

round, 212
., ship, 284

tube, 225

Xylophaga, 286
Xylotrya, 285

Yellow sponge, 64
Yoldia, 200

Ziphacantha. 11
Zimmocca sponge, 64
Zirphiea, :186
Zoantharia, 110, 116
Zonites, 312
Zonitinie, 312
Zoocytium, 40
Zoodendria, 33
Zooid, 78
Zoology, ii

,, history of. Ixiv
Zoon , 57
Zoophytes. 72
Zoothamnium. 45
Zoroaster, 100
Zygobrancliia, 319
Z'y'godactyla, 87
Zygosis, 30

^'^i>^

"ii^^i*^

mm.

0^'--,

-xr-i

'M§^

^^

.^!>:

;<^

:^,

/f^'

■^^.